Float detection system

ABSTRACT

The specification discloses a method and apparatus for detecting the position of the float in a glass tube flow meter, and determining the distance of said float from a reference line on the glass tube flow meter which is being calibrated. The blockage of an infrared light beam being sent from a transmitter to dual photo receivers, coupled to an optical conditioner circuit, provides an indication of whether float is high, low or in-band in relationship to the desired position, while a float follower, which is movable along the length of the flow tube by a stepper motor which is connected to a pulse encoder, provides through an optical conditioner circuit, an indication of the float position with regard to the reference line on the glass tube. The circuitry also provides for the automatic tracking of the float as its position is changed by the operator.

The present invention relates to a method and apparatus for calibratingflow meters and, more particularly, to a float detection apparatus foruse in calibrating such flow meters based on a variable weight-fixedtime principle, rather than on a fixed weight-variable time system,which was previously used in the art.

Present day flow meter calibration systems work on the principle ofmeasuring the time it takes a fixed weight of fluid that has passedthrough a flow meter to collect in a weigh tank which is suspended on ascale beam, which in most cases is a compound beam arrangement becauselarge flows are involved.

The compound beam arrangement has a small beam and a large beam,sometimes referred to as a "tare" and a weigh beam", respectively.Usually on the top of the tare beam is an adjustable weight to set thezero point of the scale, and on the end of the tare beam is a pan inwhich precision weights are placed by the operator. To provide the mostaccuracy possible, the beam is usually of a type known as a knife-edgebeam.

Used in conjunction with the scale is an electronic timer indicatingdirectly in units and tied to its own crystal frequency standard, forexample, a crystal oscillator.

In operation, the present state of the art systems, based on fixedvariable weight-time, would be started up before an actual test and youwould have a reservoir being supplied through a pump, a filter, a heatexchanger, and a float control valve. The fluid flowing through the flowmeter being tested would flow through the above devices, and the circuitwould be completed by a back pressure control and a conduit leading tothe pan on a weigh scale, with the weigh scale being able to dumpdirectly into the reservoir.

In these systems, because the flow of the fluid is temperaturesensitive, heat exchanger equipment would typically control thetemperature of the fluid to plus or minus 1° F., after which it wouldpass through the control valve, the meter under test, the back pressurevalve, the weigh tank and then back into the reservoir. This type ofaction would take place for a predetermined amount of time until thesystem is temperature stabilized.

A preliminary fill of the system would then take place after theoperator has adjusted the flow control valve to bring the float in theflow meter to the point at which it is desired to test such flow meter.After this flow has been established, a small weight is placed on thepan of the weigh scale, the electronic timer is set to zero, and thedump valve would be closed, starting the filling of the weigh tank.Since the placing of the weight put the scale off balance, thispreliminary fill time would end when an actuator was tripped, indicatingthe scale was again in balance.

By using the preliminary fill it should be understood that the scale isthen placed in a dynamic condition overcoming initial friction and soforth. When the scale is back in balance and a weight of fluid is in theweigh tank equal to the small weight which has previously been placed onthe weigh scale, the actual weight desired to be measured is placed onthe weigh pan, again deflecting the beam. Since the timer had also beenreset when this scale reached its balanced condition, it can be seenthat the timer is now actually counting the amount of time necessary forthe scale to again reach its balance condition, or, in other words, theamount of time for a predetermined amount of weight to be flowed intothe weigh tank. The timer will lock when the scale is again in balance,after which time the dump valve on the weigh tank will open, allowingthe fluid to pass through to the reservoir and complete the cyclepreviously described. Such variable time-fixed weight systems have haduseable accuracy at high flows over many years of service. While suchaccuracies were satisfactory for applications existing up to the presentday, increased technology, and the move to economical operation of suchthings as gasoline engines, and their being of even smaller sizes, hasbrought to the forefront the need to measure even smaller flow rates atever greater accuracy.

Applicant's assignee has been a manufacturer of carburetor testingequipment who has been directly involved in the testing of automotivecarburetors for many years, and has seen the flow rate for automotivecarburetors decrease from several pounds per hour to as low as one-halfpound per hour and, in order to test carburetors at such low flows, itis necessary to have more accurate flow meters than were heretoforeavailable. Applicants, therefore, several years prior to the presentapplication, have had to recalibrate flow meters calibrated by the oldfixed weight-variable time system, since such system simply was notaccurate enough to calibrate flow meters to the accuracy necessary forthe present day requirements, such as carburetors of smaller and smallerengines.

Applicants' assignee attributed the failures of the fixedweight-variable time system to several reasons. First of all, a seriousproblem was inherent in the system. When one wished to calibrate a flowmeter at a certain spot, the operator of the calibration system, bymeans of a hand valve, brought the float to a certain level and had tomanually keep it there throughout the test. When large flow wasinvolved, things which were found to affect the movement of the float atlow flows, such as pulsation inherent in the previously mentioned pump,were not present, and the operator could fairly accurately "eyeball" thefloat level. However, it was found that when low flows were attemptedwith the same setup, say flows below five pounds per hour, thepulsations present in the flow because of the type of pump made thefloat move so much that the operator simply could not eyeball it to theproper level with any degree of accuracy and the system provided norepeatability whatsoever.

Thus, the eyeballing problem and the repeatability problem were two ofthe problems which led Applicants' assignee to abandon the fixedweight-variable time system. Other problems that were found to existwere frictional problems inherent in the weigh scale used in suchsystem. Since such prior art systems were mainly used for large flows,which necessarily resulted in a large weight being accumulated in theweigh pan in a short period of time, the frictional effects on theaccuracy of the measurements were negligible. However, again, whenflowing below five pounds per hour, it was found that the frictionaleffects of the scale had a significant effect on the measurements.

Another problem which was found was related to the previous eyeballingproblem, in that the physical limitations of the operator in eyeballingthe float to the proper position meant that rather large separationsbetween graduations on the flow meter were a necessity. Again, whenlarge flows were involved this was no problem, but when low flows (belowfive pounds per hour) were used, these large distances betweengraduations represented large differences in flow, and the improvedreadability needed at low flow simply was not achievable.

Applicants, despite many attempts, found that attempting to overcome thefailings of the fixed weight-variable time flow meter calibrationsystems were futile because of their inherent nature and thus,Applicants had to abandon the fixed weight-variable time system andattempt to solve the problems of flow meter calibration, based on theonly other physically possible type of system, that being one based on ameasuring a weight for a fixed period of time, known as a variableflow-fixed time system.

Thus, one of the objects of the present invention is to provide a flowmeter calibration system operating on the variable weight-fixed timetheory of operation.

Another object of the present invention is to provide a flow metercalibration system capable of calibrating all types of flow meters usedin the art today, such as rotary flow meters, turbine flow meters andglass tube flow meters.

Another object of the present invention is to provide a flow metercalibration system useable for calibrating flow meters having very lowflow rates.

Another object of the present invention is to provide a flow metercalibration system of the foregoing nature which can calculate flowmeters to one quarter percent accuracy or better.

Another object of the present invention is to provide a flow metercalibration system capable of calibrating flow tubes, or other flowmeters, and providing such calibration with a high degree ofreadability.

A further object of the present invention is to provide a flow metercalibration system for a glass tube flow meter which removes theoperator from the position of having to maintain the flow meter float atan accurate position in the flow meter.

A further object of the present invention is to provide a flow metercalibration system which eliminates the effects of scale friction fromthe results of the calibration.

A further object of the present invention is to provide a flow metercalibration system which eliminates the effects of pulsating flow fromthe calibration measurements.

A still further object of the present invention is to provide a systemin which the float in a glass tube flow meter is followed by anautomatic tracking device.

A still further object of the present invention is to provide acalibration system having a digital readout of float position versus areference line on the flow meter tube, so that the float position may bemarked on a scale at a later time with great accuracy.

A further object of the present invention is to provide a flow metercalibration system capable of calibrating flow meters adapted to measureminute flows.

A further object of the present invention is to provide a flow metercalibration system of the foregoing nature which is dependable andrepeatable in operation.

Further objects and advantages of this invention will be apparent fromthe following description and appended claims, reference being had tothe accompanying drawings forming a part of this specification, whereinlike reference characters designate corresponding parts in the severalviews.

FIG. 1 is an artist's rendition of a laboratory installation containingone or more constructions embodying our improved flow meter calibrationsystem.

FIG. 2 is a perspective pictorial view of the electronic controlinstrumentation used to operate constructions embodying our invention asthey may be installed in the control room of FIG. 1.

FIG. 3 is a perspective pictorial view of the actual calibrationequipment embodying the construction of the present invention.

FIG. 4 is an elevational view of the control panel of the equipmentshown in FIG. 2.

FIG. 5 is a view illustrating the proper arrangement of FIGS. 5A, 5B and5C to show the overall diagrammatic arrangement of our improved flowmeter calibration system.

FIG. 5A is a diagrammatic view showing the control subsystem of ourpresent invention which supplies means for controlling the plant airsupply, the plant water supply and the fuel supplied to the presentinvention.

FIG. 5B is a diagrammatic view showing the detection subsystem of thepresent invention, which supplies a means for detecting the currentoperating condition of the flow meter being calibrated, and themonitoring subsystem, which supplies a means for monitoring the physicalcondition of the media being calibrated.

FIG. 5C is a diagrammatic view showing the weigh scale subsystem of thepresent invention.

FIG. 6 is a drawing showing the arrangement of FIGS. 7 and 8 to show therelationship between FIG. 7, showing the float detection subsystem ofour present invention, and FIG. 8, showing the weigh scale subsystem ofthe present invention.

FIG. 7 is a block diagram of the float detection control circuit shownin FIG. 11.

FIG. 8 is a block diagram of the time weight scale control and timingcircuit shown in FIG. 10.

FIG. 9 is a drawing showing the arrangement of FIGS. 10 and 11 to showthe relationship between FIG. 10, which is a diagrammatic view of theweigh scale subsystem of the present invention, and FIG. 11, which is adiagrammatic view of the float detection subsystem of the presentinvention.

FIG. 12 is a block diagram of the electrical controls necessary tocontrol the flow of air, water and fuel through the control subsystemsshown in FIG. 5A and a portion of FIG. 5C.

FIG. 13A represents a portion of the fuel injector circuit shown in FIG.12.

FIG. 13B represents the remaining portion of the fuel injector circuitof FIG. 12.

FIGS. 14A and 14B are drawings of the circuit corresponding to FIGS. 13Aand 13B as actually built.

FIG. 15 is a block diagram of the electrical circuitry necessary tooperate the supply subsystem shown in FIG. 5C.

FIG. 16 is a block diagram of the monitoring system disclosed in aportion of FIG. 5B.

FIG. 17 is a schematic diagram of the fuel pressure set circuit shown inFIG. 12.

FIG. 18 is a schematic diagram of the pressure regulator control circuitshown in FIG. 12.

FIG. 19 is a schematic diagram of the injector pressure display circuitshown in FIG. 16.

FIG. 20 is a schematic diagram of the injector solenoid driver circuitof FIG. 12.

FIG. 21A is a circuit diagram of the pretest test and clock selectcircuits of the time weight scale control and timing circuit of FIG. 8.

FIG. 21B is a circuit diagram of the clock circuit and scale cyclecontrol circuit shown in FIG. 8.

FIG. 22A is an electrical diagram of a portion of the power supplycircuit, the pulse encoder circuit and a portion of the poise controlcircuit shown in FIG. 10.

FIG. 22B is an electrical diagram showing a portion of the power supplycircuit, a portion of the poise control circuit and the encoder, asshown in FIG. 10.

FIG. 23 is a view similar to the detection subsystem shown in FIG. 5B,which may be used when a turbine flow meter is being calibrated.

FIG. 24 is a view similar to the detection subsystem shown in FIG. 5B,which may be used when a differential pressure transducer is beingcalibrated.

FIG. 25 is a view similar to the detection subsystem of FIG. 5B, whichmay be used when a linear mass flow meter is being calibrated.

FIG. 26 is a schematic view of the stepper motor driver circuit shown inFIG. 7.

FIG. 27A is an electrical diagram showing the manual select circuit, theclock circuit the clock select circuit, the auto abort circuit, thedirection polarity latch circuit and a portion of the auto selectcircuit and stepper motor translator circuit of FIG. 7.

FIG. 27B is an electrical diagram showing the travel limit circuit and acontinuation of the stepper motor translator circuit and auto selectcircuit shown in FIG. 7.

FIG. 28 is a schematic view of the travel limit circuit shown in FIG.27B.

FIG. 29 is an electrical diagram of the LED transmitter shown in FIG.11.

FIG. 30 is an electrical diagram of the receiver shown in FIG. 11.

FIG. 31 is a block diagram of the float detector display circuit shownin FIG. 7.

FIG. 32 is a block diagram of the optical conditioner circuit shown inFIG. 11.

FIG. 33 is a view showing the arrangement of FIGS. 33A, 33B and 33C.

FIG. 33A is a schematic diagram of the amplifier circuit of FIG. 32.

FIG. 33B is a schematic diagram of the decode circuit of FIG. 32.

FIG. 33C is a schematic diagram of the power supply circuit and thesynchronous modulator circuit of FIG. 33.

FIGS. 34A, 34B and 34C form a schematic diagram of the display circuitshown in FIG. 31 as actually built.

FIG. 35 is a block diagram of the time weight display circuit shown inFIG. 10.

FIGS. 36A and 36B are circuit diagrams corresponding to the blockdiagram of FIG. 35.

FIGS. 37A, 37B and 37C are schematic diagrams of the circuits shown inFIGS. 36A and 36B as actually built.

FIGS. 38A, 38B, 38C and 38D are schematic diagrams of the circuits ofFIGS. 22A and 22B as actually built.

FIGS. 39A, 39B, 39C and 39D are schematic diagrams of the circuits shownin FIGS. 27A and 27B as actually built.

FIGS. 40A and 40B are schematic diagrams of the circuit of FIGS. 21A and22A as actually built.

FIG. 41 is an elevational view of the weigh scale used in the presentinvention, and also showing the injectors used to supply the fuel to theweigh scale, as well as the extraction tubes used to remove the fuel.

FIG. 42 is a partial plan view of the weigh scale of FIG. 41.

FIG. 43 is a partial plan view of the weigh scale shown in FIG. 41showing the optical encoder, air gap transformer, counterweight and ballscrew.

FIG. 44 is a partial elevational view of the weigh scale illustrated inFIG. 41 showing the drive motor, the ball screw and the movable poiseweight.

FIG. 45 is a partial elevational view illustrating the float followerutilized in the present invention.

FIG. 46 is a plan view of the float follower shown in FIG. 45.

FIG. 47 is a front elevational view of the apparatus used to move thefloat follower illustrated in FIGS. 45 and 46.

FIG. 48 is a side elevational view of the apparatus shown in FIG. 47.

FIG. 49 is a perspective view showing a portion of the receiver.

FIG. 50 is a plan view of the receiver shown in FIG. 49.

It is to be understood that the present invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways within the scope of the claims. Also, it is to be understood thatthe phraseology and terminology employed herein is for purpose ofdescription, and not of limitation.

Applicants, in an attempt to design a flow meter calibration systemwhich would give accurate and dependable results at low flows, forexample, zero to five pounds per hour, first considered continuing touse the fixed weight-variable time system heretofore described. However,despite several attempts, while such system was satisfactory for largeflows, it was entirely unsatisfactory for low flows, and Applicants wereunsuccessful in increasing the accuracy of such system beyond a veryminimal amount, as no way was found to reduce the mechanical friction ofthe scale in a sufficient degree to eliminate that problem, or to reducethe pulsation of the fuel in such a system. Therefore, Applicantsabandoned their attempt at modifying the fixed weight-variable timesystem, and decided instead to go to a fixed time-variable weightsystem, in which the float in the flow meter, in the case where it is aglass tube flow meter being calibrated, would be set, and a flow wouldbe measured for a fixed period of time.

In doing so, Applicants still had to solve the problem of how toeliminate the operator factor in tracking the float, and how to weighthe flow through the flow meter for a fixed period of time accuratelyand without introducing the same problems of friction and human errorwhich the prior art systems had.

To eliminate the human error in the system of setting the flow meterlevel to a certain point and having the operator "eyeball" the float andcontinually adjust the valve to keep it in a fixed position, Applicants'idea of measuring the variable flow for a fixed time appeared to proveideal if it could be implemented because then the float would be set toa position, an automatic means to make sure that the position of thefloat did not vary more than an acceptable amount would be provided, andthe flow rate would vary only because of variations in the temperatureand pressure of the fluid flowing through the flow meter, etc., i.e. thesame ones which made the float vary in the fixed weight-variable timesystem and cause the operator to continuously operate the valve.However, implementing this proved difficult to achieve.

Applicants first had to design some type of mechanical tracking devicewhich could sense the position of the float and give the operator of thecalibration system an indication when the float moved more than apermissible distance. However, since Applicants were dealing with verylow flow, the flow meter tube had a very small inside diameter, andsimilarly the float itself was very small, and a device to track thefloat proved difficult to design.

Applicants first thought the position of the float could be detectedwith sound waves, such as used in the sonar principle, but this soonproved to be impractical. Having failed to achieve this based on a soundbased system, Applicants next looked to an optical device to track thefloat. However, even this proved to be very difficult to achieve becauseApplicants' first attempt, that of shooting a laser beam through theflow meter tube and detecting whether that beam passed through the tube,or was stopped by the float proved unsatisfactory because it was foundthat the glass tube refracted the laser beam in an extremely divergentmanner, making it very difficult to receive the beam on the other end ofthe tube. Also, by using the laser we could only get a single signal andwe were unable to determine where on the float the laser beam was.

Another factor which we became aware of which convinced us not to uselasers, was the fact that very high voltages were necessary, which madethem almost impossible to use in explosive atmospheres, such as would bepresent when flammable fuel was being passed through a flow meter. Also,the danger to the operator should he attempt to confirm the presence ofa laser beam from the laser convinced us that this approach should beabandoned.

However, Applicants' second attempt at an optical system provedsatisfactory, and that system, as will be fully described hereinafter,involved the use of fiber optics, where a thin beam of infrared lightwould be transmitted through the tube at a short, spaced apart, distanceto a pair of receivers placed a short distance apart on the oppositeside of the tube. The distance between the light receivers would be thetolerance within which the flow meter float would be allowed to movebefore the flow meter calibration test would be automatically aborted.

Having achieved this solution to the problem of detecting the flow,Applicants then used other well known mechanical and electronictechniques to drive the transmitter and receivers up and down the lengthof the flow tube, as needed, by the use of a mechanical ball screw whosemovement was controlled by electronics associated with the fiber opticstransmitter and receivers. This subsystem of our improved flow metercalibration system, which we choose to refer to as the float detectionsubsystem, will be described more fully hereinafter.

Having now removed the operator from the position of having to maintainthe float position, our attention then turned to how to remove theoperator from the position of weighing the flow of fuel from the flowmeter for a fixed period of time. It might appear easy to some that weshould simply let the flow, whatever it may be, pass into the bucket forone minute and then measure the same. However, we would then introduceexactly the same type of error which the fixed weight-variable timesystem had, i.e. the adding of the weight to the scale by the operator,and the time keeping function, together with, if we used the same typeof scale, the frictional problems which were present in the old system,and this simply would not be a satisfactory solution to the problem.

Based on our knowledge of scales which attempt to keep themselvesbalanced as weight is added to them by means of a movable poise weight,which, if a consideration of the balancing of moments are taken intoaccount, together with accurate calibration, means that the movement ofthe poise alone will tell you the flow into the scale during any periodof time, we attempted to go in this direction, and ultimately did, aftermaking several attempts and failing at them. Our first attempt was touse a known scale manufactured by the Tridyne Corporation whichperformed this way. This scale had the aforementioned poise weight driveby means of a ball screw and ball nut, but because this scale did nothave the drive motor directly connected to the ball screw, but had astepper motor hung below and geared to the ball screw, mechanicaltolerances were introduced which were unsatisfactory. Even though onestep of the stepper motor presumably equaled 0.00005 pounds in the weighbucket, we found that the count of the stepper motor pulses did notalways guarantee a turning of the ball screw by the correct amountbecause of the hysterisis through the gearing system.

Furthermore, the Tridyne scale still had a friction error which itintroduced into the measurements which, although much less than the oldweigh beam scale used in the fixed weight-variable time system, wasstill significant when used for very low flows, and we felt we had tohave a better weigh scale for very low flows.

In our attempts to design our own scale to overcome the deficiencies ofthe Tridyne scale, we developed the scale used in a commercial system ofApplicants' assignee described in Bulletin 6622 attached hereto asExhibit 2 in the appendix of the present application. In this system,liquid from the flow orifice being calibrated was allowed to flow intothe selected container for a pretest time to be sure that it was flowingfreely and uniformly, and then the poise weight position was noted whenthe test time was started. The liquid was measured for a fixed period oftime, for example, one minute, and then the poise position was againnoted.

By the balancing of moments principle, and calibration of the scale inadvance, the movement of the poise weight gave you the weight of theliquid which had flowed during the one minute time. Because in thisscale, the poise weight was directly driven by a stepping motor, asource of mechanical error was eliminated which was present in theTridyne scale, and this scale gave much more accurate results.

However, we discovered that there was still a source of frictional errorpresent in the scale which proved significant at low flows. This wasbecause of the wires which had to be attached to the scale to transmitpower to the poise, and to the linear variable displacement transformer,which is the signaling device which measures the actual displacement ofthe weigh pan and transmits signals to govern the speed of the movementof the poise weight to keep the scale in balance. Even though the wireswere attached in such a manner to produce a very low resistance tomovement, at low flows this resistance was felt, and had to beeliminated. Thus, we had to perform further work on this scale toeliminate this source of error, and developed the idea of transmittingpower to the various components of the scale through an air gaptransformer to prevent the frictional error in the previous scale.

This coupling, and the scale to be described more fully hereinafter,have become known in the art as a separate entity and are describedherein by Exhibit 3 to the appendix of the present application. However,the use of such scale in a flow meter calibration system is novel, andhas solved the problems long standing in the prior art of how to obtainan accurate reading of flow over a fixed period of time with the leastpossible error.

Having arrived at a satisfactory weigh scale, the remaining source oferror discussed in connection with the prior art flow meter calibrationsystems was the error introduced into the system by the pulsating of theflow as it came into the weigh pan. As mentioned previously, when largeflows, such as 3,600 pounds per hour were involved, such pulsations wereabsolutely negligible and did not effect the results. However, at lowflows a significant effect was discovered not heretofore known in theart, and we had to find a way such that the kinetic energy which thepulsations represented would be absorbed before the flow was allowed togo into the weigh pan.

We knew that we could not completely eliminate the pulsation problemwith any device that we used, but determined that placing fuel injectorsbetween the pump and the weigh pan, together with a kinetic energyabsorption device, which was in turn placed between the injectors andthe weigh pan, we could reduce the problem to practically zero,especially if we were to establish a flow of fluid through the injectorsand the kinetic energy device to make certain that the fluid was flowingfreely and uniformly, and couple this device with an evacuation tubeassembly which would remove the fluid as fast as it was flowing in andmaintain the fluid at a tare level for the pretest, and then have thetest start with the evacuation tubes being removed simultaneously withthe test starting so that any effects on the scale would be minimized,appear to solve this problem of kinetic energy for low flows. Thus, byusing a combination of a float detection system, an evacuation tubesystem, and a weigh scale system, we have eliminated problems longstanding in the art which heretofore completely prevented accuratecalibration of flow meters at flows in the range of zero to five poundsper hour.

It, of course, is to be understood that our flow meter calibrationsystem can be used for any flow rate, including the very large flowrates which prior art calibration systems were used for, and still bewell within the scope of the present invention. We only wish it knownthat, as stated in the objects of our invention, we encountered andsolved many problems long standing in the art because our particularapplication was for the minute flows which are needed in the present daytechnology.

To complete our solution to the problem of accurately measuring lowflows, we were determined to control the ambient variables to a closerdegree than was heretofore done in the prior art. As already mentioned,since it is volumetric flow which is being measured, the calibrationpreferably should take place in a temperature controlled room, and thisinvolves the supplying of temperature control systems well known in theart.

We have also provided for humidity and pressure control to increase theaccuracy of this system, although, of course, one could use the systemwithout such temperature, pressure and humidity controls if desired.

In order to provide the constant temperature and humidity which oursystem needs to operate properly, we prefer to have a specialinstallation for its use, although it is to be understood that thiscertainly is not necessary. We provide, as shown in FIG. 1, a buildinghaving several rooms specially adapted for use in calibrating flowmeters. Such building may be generally referred to as the calibrationfacility 50.

In the calibration facility, one may find such rooms as a control room,generally designed by the numeral 51, having therein (referring to FIG.2) one or more power supplies 53, and one or more control consoles 52used in our invention, and to be more fully described below. The controlroom 51 may also contain, if it is desired to operate our system bycomputer control, a isolated computer room 54 having a computer 55enclosed therein.

Preferably adjacent the control room 51 is a flow room, generallydesignated by the numeral 56, containing one or more calibrationapparatus generally designated by the numeral 58, and one or more weighscale apparatus, generally designated by the numeral 57 (see FIG. 3).

As illustrated in FIGS. 2 and 3, suitable electrical connectionsindicated by the numeral 59 are made between the power supplies andcontrol consoles, and the calibration and weigh scale apparatus.Depending on the type of flow meter being calibrated and the fluid whichis being used to calibrate the flow meter, it is well within the scopeof the present invention that some type of special electricalconnections may be needed. For example, some types of fluid used tocalibrate a glass tube flow meter, such as indoline or gasoline, arerather volatile and thus flammable, and all electrical connections mayneed to be made to code, which requires them to be explosion proof.

Since how to make these electrical connections is known to those skilledin the art who must deal with these codes, and such connections are notalways necessary depending on the type of flow meter being calibratedand the fluid being used, it is not felt necessary to describe suchconnections further herein. It should be understood though, that theyshould be used with our invention where required.

Since it is contemplated by the inventors that their system often willbe used with such fluids as indoline and gasoline, even though thespecific electrical connections between the control room and the flowroom have not been shown with specific types of interlocks which may berequired by local codes, the system has been illustrated with somecommon safety features which it is believed will be needed. For example,the electrical connections 59 are shown enclosed in conduit, and thecalibration facility 50 would be equipped with a fire extinguisher dumpsystem (such as Cardox). Also, the fluid to be used in the system wouldbe stored in a separate fuel room 61, with excess fuel being stored inan underground bulk storage yard 62. All of the mechanical equipmentnecessary to provide temperature and humidity conditioned air and fuelat as close a constant temperature as possible is kept in a separatemechanical room generally designated by the numeral 63, with a hallway64 provided between the mechanical room and the control room, fuelstorage room and flow room.

In the mechanical room 63, depending on the particular needs of theuser, will be various equipment. Contained in the mechanical room 63 aresuch things as a water purification system 65, a humidity control system66, a heating system 71, an air compressor 67 and an air conditioningpackage 68.

For safety purposes, there are illustrated a number of flash detectors69 and Cardox discharge bottles 70, which would be in the flow and fuelrooms.

Referring again to FIG. 3, in accordance with our method, the operatorof the system embodying our invention will set, with the aid of thecontrol panel 79 mounted on the control console 53, a constant flow offluid to one of the glass tubes 78 in the glass tube flow meter 60, withthe aid of the weigh scale 77. This will cause the float follower 93 tofollow the float (not shown) in the glass tube 78 to a certain heightwhich can be measured from a fixed reference point, and then when theflow is calculated for a fixed period of time, for example, one minute,the flow rate which the operator established will be known, and thedistance of the float from a fixed reference point on the tube 78 willhave been established.

Subsequent to this, a scale can be made having as a zero point the fixedreference point on the tube, and the different flows can be marked onthe scale at different points from the fixed reference point, which willthen correspond exactly to the position which the float was at when theflow was established by the system operator.

In a method to be more fully described later, the operator has variousways to set the float in the tube at different heights by varying theflow rate. Since we use injectors in our invention to establish the rateof flow through the flow tube and the weigh scale, the operator may turnon one or more of these injectors by means of the injector switches 81(FIG. 4) having thumbwheels 81A thereon. When the injectors are off, thereadings on any of the switches will read 00, and turning thethumbwheels to a reading from 01 up to 99 will tell you the percentageof time that the particular injector is on.

Also, the operator has the choice of varying the frequency of theinjectors themselves by varying the setting on the period switch 84.Also available to the operator is a means for adjusting the pressure ofthe fluid flowing through the flow meter by means of the pressure adjustpotentiometers 83 and 83A.

Before disclosing the preferred method in more detail, it is necessaryto have a greater understanding of the apparatus which is needed tosupply the temperature and humidity conditioned air, and the temperatureconditioned fuel, to our flow meter calibration system.

Referring now to FIGS. 1, 5, 5A, 5B, and 5C, there is shown a fluiddiagrammatic view of our entire flow meter calibration system. Thesystem itself is divided into five subsystems, and these can beidentified as the supply subsystem, generally designated by the numeral85, the control subsystem, generally designated by the numeral 86, themonitoring subsystem, generally designated by the numeral 87, the weighscale subsystem, generally designated by the numeral 88, and the flowdetection subsystem, generally designated by the numeral 89.

It should be understood, as previously described, that our invention canbe used to calibrate many types of flow meter devices. Although thepreferred embodiment is described for use in calibrating a glass tubeflow meter, which is the most common type of flow meter presently used,it can also be used to calibrate turbine flow meters, single or multipleorifice flow meters, and linear mass flow meters. For this reason wehave labeled the box in FIG. 5B a flow detection subsystem, generallydesignated by the numeral 89, so that the flow detection subsystem inFIG. 5B could be replaced by the various flow detection subsystems shownin FIGS. 23, 24 and 25. For example, a system for detecting flow througha turbine flow meter carries numeral 89B, while a system used for asingle or multiple orifice flow meter carries numeral 89C, and a systemused for a linear mass flow meter carries numeral 89D.

Referring to FIG. 5B, when, as in the preferred embodiment, ourinvention is to be used to calibrate a glass tube flow meter, the flowdetection subsystem 89 will include a stepper motor 95 operating a ballscrew 96 which is attached to an optical encoder 97 to provide a readout98. Attached to the ball screw 96, in a manner to be more fullydescribed hereinafter, are a receiver 99 and a transmitter 100 ofinfrared light which is adapted to track the position of the float 101in the glass flow tube 78.

Referring to FIG. 23, there is a turbine flow meter system 107,including generally the well known components of a turbine flow meter,outputting a signal to a frequency counter 103 which is then operated onby a K-factor circuit 104 and a linearized specific gravity andviscosity circuit 105 to produce a flow readout 106. Such turbine flowmeter systems are well known in the art and need not be describedfurther herein.

Where our invention becomes useful for manufacturers of turbine flowmeters is to obtain a relationship between the frequencies counted bythe frequency counter 103 and the actual flow through the turbine flowmeter 102 and, in this case, our flow detection system 89B will comprisethe turbine flow meter 102, the frequency counter 103 and a readout103A. As before, a flow will be set up through the weigh scale apparatusin a manner to be more fully described hereinafter, and will be takenfor a fixed period of time and will be determined. Such determined flowwill, of course, have a related frequency reading, and the turbine flowmeter manufacturer, then having a table of frequency counts related toflow through the turbine flow meter can determine values needed for theK-factor circuit and the linearized specific gravity and viscositycircuit to give a linear flow readout through the turbine flow meterreadout 106 in engineering terms.

Similarly, now referring to FIG. 24, there is shown a single or multipleorifice flow meter system generally designated by the numeral 108, andincluding generally a single or multiple orifice flow meter 109 whichtransmits a differential pressure signal to the differential pressuretransducer 110. Since the differential pressure transducer 110 gives anoutput in the form of a square root function, a circuit known in the artis needed to extract the square roots from the signal to provide anominally linear function, which is further operated on by thelinearizer circuit 113 to provide a linear signal to the single ormultiple orifice flow meter readout 114.

To enable the manufacturer of the single or multiple orifice flow meterto choose the right functions to provide an accurate readout, a tablegiving the relationship between the actual flow through the flow meter109 and the signal produced by the differential pressure transducer isneeded, and our system can give just such a table by considering ourflow detection subsystem to be the box labeled 89C. As before, aconstant flow is established through the weigh scale apparatus 57 atseveral different flows which have several different correspondingoutputs of the differential pressure transducer and, therefore, a tablecan be produced relating its specific flow to a pressure transducersignal as read on the readout 110A.

Our system can also be used to calibrate the well known linear mass flowmeter or hydraulic wheatstone bridge known under the tradename"Flotron". Such a system, generally designated by the numeral 116,consists of the linear mass flow meter 117 which, as illustrated,generally consists of four orifices and a pump. A pressure reading istaken across the inlet and the outlet of the wheatstone bridge andsupplied to the linear mass flow meter differential pressure transducer118.

That signal, to aid in obtaining a linear readout, is operated on by theknown signal conditioner 119 and that result is supplied to the linearmass flow meter readout 120. Again, our system aids in calibratinglinear mass flow meters by giving a table of values of actual flowthrough the linear mass flow meter related to the differential pressuretransducer.

In this case, the signal conditioner 119 is mainly to convert the signalfrom the differential pressure transducer from the voltage signalreceived therefrom to a reading in engineering units, but it iscontemplated that such signal conditioning circuit could also be used tomake any corrections necessary if the linear mass flow meter, as shownby calibration on our equipment, turned out to be not exactly linear andsome corrections were needed.

Now returning to FIG. 5B showing the flow detection system used tocalibrate a glass tube flow meter, which is the preferred embodiment ofthe present invention, an explanation of the diagrammatic view of oursystem consisting of FIGS. 5A, 5B and 5C can be understood. As can beseen by referring to FIGS. 5A, 5B and 5C, the float detection subsystem89A is shown contained within the monitoring subsystem 87. Of course, itis to be understood that this is only for the purpose of illustration,and it could have easily been drawn outside the boundary lines of themonitoring subsystem.

Since it is the fuel passing through the meter 60 (FIG. 3) which causesthe movement of the float 101 within the glass tube 78, the travel ofthe fuel throughout our fuel flow calibration system shall first bedescribed. In order to supply an ample amount of fluid for operation ofour system, a fuel storage tank 124 (FIG. 5C) is provided. Since thetank must accept returns of excess fluid from various parts of thesystem, a tank return 122 is connected to a first shut-off valve 123,and then to the tank 124.

A second shut-off valve 125 is placed immediately downstream of the tankfor shutting off fuel flow through the system when it is in itsinoperative state. Following the shut-off valve, to make certain that noimpurities are left in the fuel, is a strainer 126, which is thenconnected by suitable conduit to the pump 127 driven by the motor 128.Also, in the supply subsystem is an evacuation pump 129 driven by theevacuation pump motor 130 which, as just described, returns fluid to thetank through the tank return 122. This will be described in more detailbelow.

Since our system is useful in calibrating a wide range of sizes andtypes of flow meters, the pump 127 must be large enough to accommodatesuch variety. However, we also do not want to allow the pump to becomeoverloaded and, for this reason, want to set the maximum pressure in thesystem somewhat below the maximum possible output of the pump 127.Therefore, after the fuel passes through the pump 127 and the fuelfilter 131, it is passed through the back pressure regulator 132, whichis set to have an output readable on the back pressure meter 133,attached to the regulator 132, somewhat less than the maximum output ofthe pump.

After this first stage of pressure reduction, it is desired to bring thepressure of the fuel down to that useable in the system, since we aredealing with a glass tube flow meter and anticipate dealing mostly withlow flows in such flow meters, we like to operate our system at a verylow pressure, for example, from zero to three pounds per square inch.

To reduce the fuel pressure to the pressure actually useable in thesystem, since we may have an operating range of from zero to thirtyp.s.i. which must remain extremely stable throughout that range, we havefound it necessary to use an air operated pressure regulator such asTwin Bay Model No. TB 100 V. To operate that regulator 137, since it isa one-to-one device, air must be supplied to the top end of theregulator in a range of zero to thirty p.s.i. in order to have an outputof zero to thirty p.s.i., and to supply that range of input to theregulator and to allow it to be controlled electrically from the panel79 by the pressure adjustment potentiometer 83, it is necessary toconnect the air operated pressure regulator 137 to a ratio relay 136.

To enable an output of zero to thirty pounds from the ratio delay, it isnecessary to have a constant input from the plant air supply to shut-off145, and therethrough to air pressure regulator 134, to the top end ofthe ratio relay, and to have the variable pressure, once the ratio isset into the ratio relay 136 by the ratio adjustment knob 136A,determined according to the formula: Output=d divided by c, where is cis a setting of the ratio adjustment knob 136A, and d is the variablepressure coming from the current to pressure regulator 135, which hasbeen previously set by the pressure adjustment potentiometers 83 and83A.

To enable operation of the current to pressure regulator, air must besupplied at a predetermined pressure from the plant air supply throughthe plant air supply shut-off valve 145, through the air pressureregulator 134. This then allows the pressure downstream of the airoperated pressure regulator to be set to the pressure desired for use inthe system.

Next, the temperature of the fuel must be set at a temperature useablein the system, which ideally is the temperature in the flow room 56. Itis also preferably with the temperature of the fuel be set after itspressure is regulated, because otherwise the drop in pressure wouldcause further changes in temperature, which would be undesirable in thesystem.

To set the temperature of the fuel at the desired temperature, which ispreferably the temperature to which your flow room 56 is set, to preventadditional temperature change problems, it is first passed through aheat exchanger 138. The heat exchanger is a device well known in the artwhere a fluid from an outside source at the desired temperature ispassed in a closed-loop system through a device which the fluid whosetemperature it is desired to set is also passed. In this case, the fluidflows through the heat exchanger 138 while being acted on from fluidcoming from the mixing valve 142, which may be such as Model No. 753manufactured by Research Control Corporation.

The temperature of the flow through the mixing valve is controlled by afeedback circuit. The mixing valve 142 is supplied with hot and coldwater from the plant water supply through the cold and hot watershut-off valves 140 and 141 respectively. The temperature of waterleaving the mixing valve 142 and entering the heat exchanger 138 iscontrolled by the temperature controller 144, which may be such as ModelNo. 43AP-PA42C/PC manufactured by Foxboro Corporation, in combinationwith the temperature tkransmitter 143, which may be such as Model No.43C-AN manufactured by Foxboro Corporation.

The desired temperature is initially set by the temperature control knob144A, and the temperature of the fuel leaving the heat exchanger issensed by the temperature sensor 139, which may be such as Model No.E119ZC manufactured by Foxboro Corporation. If there is any variation inthe fuel leaving the heat exchanger 138, this is sensed by thetemperature sensor 139, which sends a signal to the temperaturetransmitter 143 which, in turn, will supply a correction signal to thetemperature controller 144, which changes the setting of the mixingvalve 142.

To enable operation of the temperature transmitter, which is pneumaticin nature, plant air is again supplied to the plant air shut-off 145through an air pressure regulator 134, to the temperature transmitter.Since it is desirable to have a constant flow of water through the heatexchanger, the cold and hot water shut-off valves 140 and 141 arenormally left open, and the flow of the water through the heat exchangeris shut-off electrically by the heat exchanger solenoid 138A.

After the fuel has been conditioned as to temperature, it is now readyto enter the float detection system 89A (FIG. 5B). Since, however, thefloat detection system is at least some distance from the heatexchanger, a second temperature sensor 147 measures the temperature ofthe fuel just before it enters the flow meter undergoing calibration.

In order to be certain the system described so far, together with thesystems for controlling room air pressure, temperature, and humiditypreviously described, are working properly, there is also provided aflow room temperature sensor 148, a control room temperature sensor 149,a downstream temperature sensor 150, and an injector pressure sensor151. The second temperature sensor 147, the flow room temperature sensor148, the control room temperature sensor 149 and the downstreamtemperature 150 can be selectively displayed on the temperature display152.

The value obtained by the injector pressure sensor 151 is outputted tothe display circuit 155, which converts the signal into a signal useableby the injector pressure display 156.

The fuel is now ready to enter the glass flow tube 78 which is beingcalibrated. The flow tube is provided with a reference mark 158 to whichthe operator brings the float follower 93 until he gets a signalindicating perfect alignment. The operator then sets the optical encoderreadout 98 to zero.

In a manner to be more fully described, the operator will then setvarious flows through the glass tube flow meter, which the floatfollower 93 will follow, and the optical encoder readout 98 willindicate the position of the float with regard to the reference mark foreach flow. The operator, after having taken enough of these readings offlow in regard to the reference mark, can calibrate a flow meter scaleand mount it in the flow meter in which the glass tube 78 is mounted,with regard to the same reference mark, and thus produce a calibratedglass tube flow meter.

In order to determine the flow through the flow meter at these variouspositions according to our method, it is necessary to establish aconstant flow and measure it for a fixed period of time. As explainedpreviously, this is in contrast to systems old in the art which operatedon the basis of fixing the weight and measuring a variable time of flowuntil that weight of fluid flowed into a weigh pan. This is accomplishedby our weigh scale subsystem 88.

The flow coming through the glass tube 78 must now be measuredaccurately and in a manner so as to eliminate the inaccuracies presentin measuring in the systems old in the art. Depending on the flow rateof the fuel, such fuel will either be supplied to one or more of thesmall injectors 159, or the large injectors 160. These injectors willeither flow into a low flow gathering device 161, or a high flowgathering device 162, which are representive of devices to be explainedfurther below which absorb any kinetic energy due to the force of thefluid leaving the injectors, and then allows the flow to flow either inthe low flow bucket 163 or the high flow bucket 164.

The fluid may be allowed to remain in the bucket, or may be extractedfrom the bucket by the high flow extraction tube 165, or the low flowextraction tube 166, which are raised or lowered into the bucket bymeans of the tube bracket 167 being reciprocally raised and lowered bythe extraction cylinder 168. The fluid being removed from the bucketswhen the extraction tubes are lowered is selectively removed from onetube or the other by means of the extractor solenoid valve 169 whichselects the tube from which the fluid will be removed, and this fluid isremoved by means of the extraction pump 129 being operated by the motor130 and returned to the tank return 122. Thus, we provide for theremoval of the kinetic energy of the fluid as a source of error.

We further provide for removal of inaccuracies in the system byproviding for all electronic connections to be made by an air gaptransformer, to be described, which provides for the removal of any dragon the scale, such as was present in the old scales using magneticswitches.

We also provide for the scale to be very accurately calibrated inadvance so that each position of the poise weight 171 is related to aposition of the ball screw 170, which is driven by the drive motor 173.The optical shaft encoder enables us to know the precise position of thepoise weight as a function of the number of revolutions of the ballscrew 170. In this way, no matter what weight is placed on the scaleplatform, the amount of weight on the scale, since the poise weight willautomatically travel to a position to bring the scale in equilibrium,will always be known.

We have now solved the problems of the pulsating flow and evaporation ofthe fluid being measured at low flows by providing for measurements ofthe flow into the scale in a dynamic fashion, in which we establish aflow into the scale and continually move the poise weight at a rate tokeep the scale in equilibrium while the fluid is flowing into thebucket. We also drastically minimize the effects of kinetic energyerrors due to dripping of the fluid into the tank at very low flow ratesand minimize the evaporation which could take place with volatile fluidsat low flows. The reason that this occurs, is due to the dynamicoperation of the scale and the integrating effects of the electronics,wherein the poise weight is constantly moving as the flow is going intothe scale buckets, thus averaging out the effects of the drippings intothe bucket.

The evaporation is minimized by weighing at the same time that you areflowing into the bucket. Because you are not having to wait a finiteamount of time after the flow occurs before you weigh the amount in thebucket. Also, you are not having to move the bucket in any way before itis weighed, which could make the possibility of an air current dissipateany evaporative fumes which may be present, and this effect may befurther eliminated with very low flows by providing covers on thebuckets, etc.

The electrical controls necessary to operate the supply subsystem can beseen by reference to FIGS. 4 and 15. Power is supplied to the entiresystem by the key lock on-off switch 178. The fact that the system hasbeen activated is indicated by the illumination of the pilot light 179.

For operator convenience in starting and stopping the system, other thanat the beginning and end of the day, a separate off switch 180, and onswitch 181, are provided. The supply pump which supplies fuel to thesystem is turned on and off by the supply pump on-off switch 182, whichis connected to the supply pump relay 183, which is, in turn, connectedto the supply pump motor 128.

Similarly, the evacuation pump motor 130 is operated by the evacuationpump on-off switch 184, which is connected to the evacuation pump relay185, which, in turn, is connected to the said evacuation pump motor 130.

The fuel boost solenoid is connected similarly, having a fuel booston-off switch 186 connected to a fuel boost relay 187 which is, in turn,connected to said fuel boost solenoid 176.

To complete the discussion of the electrical controls needed to operatethe supply of subsystem of the present invention, there is provided anemergency stop switch 188 which will cutoff all power to the systemshould the occasion arise. It is to be noted that the emergency stopswitch 188 is mounted on the control panel for ease of operation by theoperator in the control room 51. For safety purposes, it is felt thatthe operator in the flow room 56 should also have a means for turningthe system off in case of an emergency and, for this reason, theemergency off switch 189 is provided, which is mounted with the controlsfor the float follower 93 in remote control panel 395.

The electrical controls necessary to operate the control subsystem ofthe present invention can be seen by referring to FIGS. 4, 5C, 12, 13A,13B, 14A, 14B, 17, 18 and 19.

Referring first to FIGS. 4, 5C and 12, it can be seen that the fuelpressure set or adjust potentiometers are indicated by 83 for the coarseadjust potentiometer, and 83A for the fine adjust potentiometer. Theseare connected to the pressure regulator control circuit 193 shown ingreater detail in FIG. 18, while the potentiometer circuit is shown ingreater detail in FIG. 17. The pressure regulator control circuit 193is, in turn, connected to the current to pressure regulator 135 toperform the functions previously described.

The fuel temperature function is initially started by the operatordepressing the fuel temperature on-off switch 195 which supplies powerto the fuel temperature transmitter 143. A signal is received by thetransmitter from the fuel temperature RTD probe 139 and this, in turn,causes a transmitter 143 to supply a signal to the fuel temperaturecontroller 144 to perform the functions diagramed in FIG. 5C.

The depressing of the fuel temperature on-off switch 195 also suppliespower to the solenoid relay 194 which operates the relay, when desired,to operate the heat exchanger solenoid 138A, to open the solenoid valveand permit flow to start through the heat exchanger 138. As previouslydescribed, the operator can set predetermined flow through the flowmeter being calibrated by turning on or off one or more injectors, andthe injector on-off switch would be depressed first by the systemoperator, which would then supply power to the high flow-low flow selectswitch 197, which would select either the operation of the smallinjectors 159, or the large injectors 160 by operation of the fuelinjection control circuit 198 and the injector solenoid driver circuit199.

The operator, to obtain the wide range of flows necessary forcalibrating all sizes of flow meters, can control the injectors as toperiod, defined as the reciprocal of the frequency, and as to the dutycycle within that period. For example, if the frequency was to be onehundred cycles per second, the period would be one one hundredth of asecond, which means an individual injector would be turning on every onehundredth of a second. The duty cycle tells you what percentage of thatperiod the injector would actually be flowing fuel. For example, if theswitches 81 were set for a duty cycle of 50%, that means the individualinjector would be on 50% of one one hundredth of a second, or theinjector would flow for one two hundredths of a second. These signalsare sent to the injector driver circuit 199 and to the injectors 159 and160 by operation of the fuel injector control circuit 198 which will bemore fully described.

A more detailed drawing of the pressure adjustment potentiometer 83 isshown in FIG. 17. As can be seen, the pressure adjustment potentiometerconsists of a one thousand ohm coarse adjustment potentiometer, and aone hundred ohm fine adjustment potentiometer connected in series withthe ground leg of the coarse adjustment potentiometer 200, and acting asa variable resistor. This results in the needed resistance across thecoarse adjustment potentiometer to affect the signal being supplied tothe pressure adjustment circuit 193, which is shown in greater detail inFIG. 18.

It should be understood that while we have given the actual values ofthe potentiometers which are used in the preferred embodiment of ourconstruction, depending on the user requirements of our system,different values for the potentiometers may be desirable, and thesevalues, as well as other values which will be discussed in the circuit,must be determined by the user of the system, depending on theparticular application for which our flow meter calibration stand isintended.

Since we must have accurate regulation by the current to pressureregulator which, as discussed in relation to FIG. 5, is active incontrolling the fuel flow through the flow meter being calibrated, weneed a very stable current to be supplied to said current to pressureregulator 135. This is done by the pressure regulator control circuit193 which utilizes a regulator circuit consisting of a series droppingresistor 207 connected between positive system voltage and the cathodeof a zener diode 206, with the anode of the zener diode connected toground. Also connected to the cathode of the zener diode 206 is one endof a limiting resistor 208. This combination of components is known inthe art as regulator circuit, and supplies a very stable voltage to thecourse adjustment potentiometer 200 previously discussed in relation tothe pressure adjustment potentiometer 83. Once this very stable voltageis acted on by the coarse adjustment potentiometer 200, and the fineadjustment potentiometer 201, it is supplied to the positive input ofthe operational amplifier 204.

The output of the operational amplifier 204 is connected to the base ofthe follower transistor 205. The negative input of the operationalamplifier 204 is connected to the emitter of said follower transistor,while the collector of the follower transistor 205 is connected to inputof the current to pressure regulator 135, and to complete the pressureregulator control circuit 193, a scaling resistor 209 is also interposedbetween the emitter of the follower transistor 205 and ground. Thus, ameans is provided for providing a very stable voltage to the current topressure regulator for accurate control thereof.

It can be seen also that in the circuit 193, the other input of thecurrent to pressure regulator is connected to the power supply at thesame point that the series dropping resistor 207 is, and that theoperational amplifier 204 must also be connected to the positive side ofthe power supply and to ground.

A more detailed illustration of the fuel injector control circuit 198can be seen by referring to FIGS. 13A and 13B. It will be rememberedthat as previously discussed, the operator of the system, in order tohave a system capable of calibrating a wide range of flow meters, musthave the means to very precisely set a wide range of flows through theflow meter being calibrated.

Referring to FIGS. 4 and 12, it can be seen that the operator has thecapability of setting the period and the duty cycle of the fuelinjectors used. It should be remembered that there are two low flowinjectors 59 which can have their duty cycle set by the thumbwheelswitches 81A and there are four high flow injectors which have theirduty cycle set by four thumbwheel switches which can be physicallyidentical to the low flow thumbwheel switches, and are indicated by thenumeral 81A on FIGS. 13A and 13B.

The fuel injector control circuit then must have a means to operate theinjectors for a certain number of cycles per second called the"frequency", and have the capability of having the injectors on for acertain amount of time during the times per second it should beoperated. As before, if an injector is supposed to operate one hundredtimes per second, there is another useful term called "period" which isdefined as one over the frequency, and in a time unit. In other words,if it is supposed to operate at a hundred cycles per second, the periodwill be one over one hundred, or one hundredth of a second and thesystem must supply the proper signal to have the injector open every onehundredth of a second, and then supply the proper signal to tell it howmuch percentage of that time of the one hundredth of a second to be onand how much time should be off, this being called the "duty cycle".

This is accomplished by having a programable period counter circuit.Since the two small injectors 159 and the four large injectors 160 aredriven by pulses supplied from the six identical solenoid drivercircuits 199, the purpose of the fuel injector control circuit is toprovide the proper input to the six identical injector solenoid drivercircuits 199 so they are able, in turn, to operate the two smallinjectors 159 and the four large injectors 160.

Two ways are available to the operator to set the wide range of flowsthrough the injectors needed to calibrate a large range of flows. Oneway is to alter the period of the injector, and this is set on theperiod selector 84 having thumbwheel switches 81A.

The other way the operator has to vary the operation is to select theinjector duty cycle, which defines what percentage of the period theinjector will be on for and what percentage it will be off for. If theduty cycle is 10%, for example, the injector will be open for 10% of theperiod and off for 90% of the period.

In order to provide the operator the opportunity of selecting thesevalues in a convenient fashion, we provide the circuitry shown in FIGS.13A and 13B. Since the injectors are operated by pulsations, we mustprovide in our flow meter calibration system a proper amount ofpulsations through the injector to achieve the desired period and dutycycle, and we do this by first of all providing a programmable periodcounter circuit designated by the numeral 211 and a number ofprogrammable duty counter circuits equal to the number of injectors, andindicated by the numerals 213A-213F.

We have learned by experimentation that an injector period of onemillisecond is very desirable from the standpoint of operator use of ourimproved system. We provide a period switch 84 having thumbwheels 81Awhich can set integers from 01 to 99 indicating the selection of aperiod of one millisecond to 99 milliseconds. This switch provides aninput to the programmable period counter circuit which has the effect ofmodifying the output of the oscillator 210 in a desired manner.

We have found that the use of a 100 kilohertz oscillator, which givesyou a pulse every one hundredth of a millisecond, is preferred in oursystem because when the integer value entered on the thumbwheels 81A ismultiplied by the time base of the oscillator, which in this case is0.010 millisecond, you get an output from the programmable periodcounter circuit 211 equal to the output of the oscillator 210. Thisoutput is very conveniently used as the input to the preset countercircuit 215 which is adapted to multiply its input by one hundred togive a time value of the period equal to the integer selected on thethumbwheels 81A of the period switch 84. In other words, one hundredmultiplied by 0.01 millisecond gives a one millisecond output from thepreset counter circuit.

We thus now have a first output from the programmable period countercircuit equal to the time base of the oscillator 210, and a secondoutput one hundred times as great, defining the period, from the presetcounter circuit. This output is supplied as a reset signal to each ofthe six identical latch circuits 218 contained in each of the sixprogramable duty cycle counter circuits 213A-213F. The latches thenoperate to define the one millisecond period in a manner to be describedbelow.

It, of course, should be understood that depending on user requirement,the range of the period we have used in our device from 1 to 99milliseconds may change, requiring a change in the oscillator 210, andother circuit components.

To provide ease of operation in selecting the duty cycle of theinjector, or, in other words, the percentage of the period the injectoris on, we provide the six individual duty cycle select switches, allindicated by the numeral 81, in FIG. 12 and all having the integerselected on the injector duty cycle represent the percentage of time theinjector is on. For example, if ten is selected, this means theoperator, has selected that individual injector to be on for 10% of theperiod. In this case, we use the output from the programable periodcounter circuit 211 and the preset signal forming a portion of theoutput of the preset counter circuit. This signal is fed from the Qoutput of the preset pulser 217 into each of the PE inputs of thecounters 214A-214L.

Also, an output from the period counter circuit is fed into each of theclock inputs of the 214A-214L counters. The output of the 214A, 214C,214E, 214G, 214I and 214K counters are inputted to the carry in (CA)input of the 214B, 214D, 214F, 214H, 214J and 214L counters and thecarry out output of the 214B, 214D, 214F, 214H, 214J and 214L countersare fed to the set input of the latches 218A-218F forming a portion ofthe programable duty cycle counter circuit 213A-214F respectively.

The other input to the reset input of the same latches comes from thepreset counter circuit, and this has the effect of, everytime the pulseis supplied to the set input of the latch, supplying a pulse to therespective injector solenoid driver circuit to turn on its respectiveinjector. When the reset input of the latch receives a pulse from thepreset counter circuit, after an amount of time equal to the duty cycle,a pulse will be supplied to turn off the injector and the injector willnot turn on again until the set input of the latch 218 receives anotherpulse. Thus, the injectors can only be turned on at time intervals equalto the period, and be turned off a period of time after they are turnedon equal to the duty cycle, and we have supplied a means for turning onthe injectors at time intervals corresponding to the period, and a meansfor turning off the injectors at a time after the beginning of eachperiod corresponding to the duty cycle.

By referring to FIGS. 13A and 13B, it can be seen that the programableperiod counter circuit 211 consists of a pair of thumbwheel switches 84Aconnected to a pair of period counters 212. While each of theprogramable duty counter circuits consists of a pair of thumbwheelswitches 81A, each of which is connected to a duty cycle counter 214 asshown.

The preset counter circuit consists of a pair of preset counters 216connected in parallel, with the clock inputs of the counters 216connected in parallel, and the carry out output of the preset counterbeing connected in series and being, in turn, connected to the clockinput of the preset pulsers. With the Q output of the preset pulse 217,as before, being connected to the preset inputs of the counters214A-214L respectively.

The six identical injection solenoid driver circuits previouslymentioned are shown in more detail in FIG. 20. It is the purpose of theinjector solenoid drivers to take the output from the latches 218A-218Fand convert this into a signal useable by the two small injectors, eachlabeled 159, and the four large injectors, each labeled 160. Before thesignals pass from the latches 218A-218F to the injector driver circuits199 to be hereinafter described, each such signal passes through a basecurrent limiting resistor 219. Such signal then enters the injectordriver circuit 199 shown in FIG. 20. Each of the six individual injectorsolenoid driver circuits consists essentially of a Darlington transistor220.

Each transistor has an emitter, base and collector with the basereceiving the signals from the respective base current limitingresistors 219. In each of the six injector solenoid driver circuits 199,the emitter is connected to ground, while the collector is connected tothe injector through a collector current limiting resistor 221.

The collector current limiting resistors 221 are identical, regardlessof whether it is a small injectors to which the signal is beingsupplied, or the the large injectors 160. The circuitry of the injectorsneed not be described in detail because these are commerciallyavailable, and may be such as Model No. GM#1606771 manufactured byBendix Corporation as far as the small injectors are concerned, andModel No. 022-906-031A manufactured by Bosch GmbH so far as the largeinjectors are concerned.

Now referring to FIG. 16, the electrical apparatus necessary for theoperation of the monitoring subsystems are shown. The thermocouples147-150, which are commercially available, and may be such as Model No.E119ZC manufactured by Foxboro Corporation, produce a signal which maybe directly displayed on the temperature display 152, which may be suchas Model No. 412A F manufactured by Doric Co. Inc.

The injector inlet pressure transducer 151 shown in FIG. 5B must havethe signal produced thereby modified to a form useable by the injectorpressure display meter 156, which may be such as Model No. 218-28manufactured by Viatran Corporation. This is accomplished by theinjector pressure display circuit 155 which is shown in greater detailin FIG. 19.

Referring to FIG. 19, since the injector pressure display meter is, inessence, a four input volt meter needing a signal common, a power and apower common input to operate, these must be obtained from the injectorpressure display circuit. The 5-volt DC power signal to the meter isobtained by utilizing the 15-volt power available in the system. The5-volt power input to the meter 156 is obtained by connecting fourfilter power capacitors 224 across the 15-volt power available in thesystem, and then connecting a three terminal voltage regulator acrossthe capacitors as shown, with the input and common terminals connectedacross the capacitors and the output and the common then connected inseries with two further power filter capacitors to provide the 5-volt DCpower.

To provide the analog signal to the meter 156, the injector inletpressure transducer is connected across the plus 15-volt power supply asshown in FIG. 19 through a current sensing resistor 227. Since we have acurrent loop type injector inlet pressure transducer 151, the voltageacross the current sensing resistor 227, because of Ohms law, will beproportional to the current passing through said resistor. This currentis then passed through an RC filter 228 to the positive input of anoperational amplifier follower 229.

The negative input of said amplifier 229 is connected to the outputthereof. Between the output of said follower 229 and circuit common isconnected a calibration potentiometer 230 whose output forms the analogsignal supplied to the display meter 156. The power common signal to themeter 156 is simply connected to the power common available in thesystem, while the signal common input to the display meter 156 comesfrom the zero adjust circuit. Such a circuit consists of a limitresistor 231 and a zero adjust potentiometer 232 connected in seriesbetween ground and 15-volt source available in the system.

The output of the zero adjust potentiometer is connected to the positiveinput of the second operational amplifier follower 233, and interposedbetween ground and the output of the zero adjustment potentiometer are apair of power filter capacitors 224. The negative input of the secondoperational amplifier follower is connected to the output thereof, andthe output thereof forms the signal common input to the display meter156. The display meter 156, now having all four needed signals willprovide a display of pressure. It is felt that no additional discussionof the display meter is necessary, as this is a commercially availableitem.

Referring now to FIGS. 8, 10, 21A and 21B, there are shown in varyingdegrees of detail, the electronics needed to operate the weigh scalesubsystem shown in FIG. 5C. Referring first to FIG. 10, it can be seenthat there is a time weight scale control and timing circuit 250 whichis central to the operation of the weigh scale subsystem. Into thecircuit are fed signals from the power supply by the scale power on-offswitch 248, which the operator depresses when he wishes to put the weighscale subsystem in operation.

Also supplying signals to the time weight scale control and timingcircuit 250 are the pretest time select switch 245 on which the operatorselects the pretest time in seconds by operation of the pretest timeselect thumbwheel switches 245A and 245B. The signal supplied by thethumbwheel switches need not be described in detail, as these arecommercially available units, and the instructions therewith amplyinform one skilled in the art of the type of signal which may beobtained therefrom.

The operator also selects the test time on the test time select switch246 in seconds or minutes by setting the test time select thumbwheels246A and 246B. This will also supply a signal to the time weight scalecontrol and timing circuit. The units in seconds and minutes which thepretest time select switch 245 and the test time select switch 246 arein is selected by the operator by the means of the test time unit selectswitch 247 which is connected to the time weight scale control andtiming circuit 250 as shown.

The scale control and timing circuit 250, in a manner to be describedhereinafter in more detail, receives the signals just discussed and, inturn, output signals to many devices. Among them will be a signal to thedrain lift relay 239 to operate the drain lift valve 238, shown also inFIG. 5C, which physically lifts the evacuation tubes 165 and 166 out ofthe low flow bucket 163 and high flow bucket 164 as desired by theoperator, by means of the extractor cylinder 168. This occursautomatically when the cycle start button 251 is pushed.

The operator, to start the test, must push the cycle start button 251previously described, and if the test must be aborted for any reason, hehas an abort switch 252 available to him should the occasion arise. Toindicate to the operator the condition, or the status, of the mode ofthe weigh scale subsystem there are provided a cycle abort light, acycle light and a test light 254, 255 and 256 respectively. Once all ofthese signals are supplied to the time weight scale control and timingcircuit 250, this circuit can begin its operation and, in turn, supplyfurther signals to the various other circuits.

Primary among these are the circuits that control the actual weigh scaleto dynamically weigh the fuel as it is put into the flow buckets 163 or164 as previously discussed. These circuits include the power supplycircuit 258 which supplies power to the electronics of the weigh scaleand is connected to the poise control circuit 263, which is thecircuitry that keeps the scale level by moving the poise weight whilethe scale is filling with the fluid flowing through the flow meter. Thisis accomplished by means of the poise motor 262 and the linear variabledisplacement transformer 261, in combination with the encoder 260.

The encoder 260, in turn, supplies a signal to the pulse encoder circuitwhich enables one to determine the position of the scale and calculatethe weight that has been placed in the scale during the test time. Thissignal is then supplied to the time weight display circuit 264 whichmakes the calculations necessary to display the weight on the timeweight display 241. A pounds/grams select switch 244 is operativelyconnected to the time weight display circuit so that the time weightdisplay will either read in grams or pounds.

Connected to the time weight display 241 is a weigh scale display testswitch 242 which lights up all the segments of the time weight displaywhen it is depressed. Also connected to the time weight display 241 is aweigh scale reset button 243.

A more detailed illustration of the time weight scale control and timingcircuit 250 is shown in FIG. 8. As can be seen in FIG. 8, the timeweight scale control and timing circuit can be further broken down intoa scale cycle control circuit 265 which sends and receives signals viaconnections to the pretest circuit 267 and the test circuit. Connectedto the test circuit is a clock select circuit 269 which receives asignal from the test time unit switch 247 previously described on FIG.10. To enable it to supply the proper time interval to the test circuit,it receives minutes and second inputs from the clock circuit 268. Sincethe pretest time is always in seconds, seconds are directly suppliedfrom the clock circuit 268 to the pretest circuit 267 and, in turn, tothe scale cycle control 265.

All of this enables the scale cycle control 265 whenever a start cyclesignal is received from the cycle start button 251, together with a highflow-low flow select signal from the the high flow-low flow selectswitch 197 (FIG. 12) to light the cycle in process light 255, to choosebetween the high flow extractor tube 165 or the low flow extractor tube166, and to also operate the drain lift relay 239 to operate the drainlift relay 240 to remove the extractor tubes 165 and 166 from the scalehigh flow and low flow buckets 163 and 164 respective.

If for some reason an abort cycle signal is received from the abort testswitch 252, the scale cycle control 265 also has the ability to lightthe abort light 254, turn off the cycle in process light and/or the testin process lights 255 and 256 respectively, send a display hold signalto the time weight display 241 to freeze the display, and operate thedrain lift relay 239 to operate the drain lift 238 in a manner to lowerthe extractor tubes 165 and 166 into the high flow and low flow buckets163 and 164 respectively.

Also, if the test is operating normally, at some point the pretest timewill be completed, and then the test in process light 256 will light,and the cycle in process light 255 will remain lit, and at the same timea brief display reset pulse will be supplied to the time weight display241 to reset it to zero.

Assuming the test runs normally to completion, at some point the testcircuit 266 will signal the end of test, at which time the cycle inprocess light and the test in process lights are turned off, a displayhold signal is supplied to the time weight display 241 to freeze thereading thereon, a signal is supplied to the drain valve relay 240, anda signal is supplied to the drain lift relay 239 to operate the drainlift 238 to lower the extractor tubes 165 and 166 into the buckets 163and 164. For a more detailed illustration of the cycle control circuit265 to describe the manner in which the pretest circuit 267 suppliessignals to the scale cycle control circuit 265 to determine the lengthof the pretest portion of the flow meter calibration, one may refer tothe illustration of the pretest circuit 267 on FIG. 21A.

As before, the operator sets the pretest time in seconds by means of thepretest select switch 245 shown in FIG. 4 and, more particularly, bymeans of the pretest thumbwheel switches 245A and 245B which areconnected in a manner well known in the art to identical pretestcounters 270, which are adapted to include a start pretest signal andsend end pretest and pretest clock signals and receive the pretestclock.

Likewise, the test circuit 266 receives signals from the test timeselect switch 246 through the thumbwheel switches 246A and 246B whichare operatively connected to identical counters 271. The same startpretest signal which loaded the counters 270 in the pretest circuit 267is used to load the counters in the test circuit 266. The counters 271are adapted to receive the test clock signal from the second NAND gate287 which receives a signal from the cycle latch 281 everytime a signalis received from the start cycle pulser 273, which occurs when the starttest signal is applied to the reset pulser 272.

As can be seen, the same start pretest signal that loads the counters270 and 271 is also used to reset the display hold latch 283 (FIG. 21B).The display hold latch 283 is, in turn, set or turned on by the end testpulser 284, and this causes a display hold signal to be sent from thedisplay hold latch. The end test pulser will turn on the display holdlatch when a signal is received. Two things may cause the end testpulser 284 to send a signal to a display latch. Either an end testsignal coming down from the counters 271 to the end test pulser 284, oran abort test signal, which will cause a test to end at any time.

If the end test pulser 284 is activated by an abort test signal, asignal is also sent through the first inverter 288 to the set input ofthe abort latch 285, which causes an output to the abort light to besent. It should be understood that the abort latch has a reset inputwhich is dependent on the end test signal coming from the counters 271.When the counters 271 are loaded by the start pretest signal, the endtest signal is turned off, thus resetting the abort latch 285. Thus, theabort latch is continually reset, ready to receive the abort test signalat any time.

The end pretest signal coming from the counter 270 in the pretestcircuit 267 comes down and enters the clock input of the end pretestpulser 274, causing the Q output from the end pretest pulser to causethe weigh scale display 241 to reset. Such output then continues throughthe set input of the test latch, causing the Q output from the testlatch to send a test in process signal. That output is also suppliedthrough the second inverter 289 to reset the end pretest pulser 274 andenable it to receive the next subsequent end pretest signal.

When the output of the end pretest pulser 274 is providing a displayreset signal, the same output is provided to one input of the secondclock OR gate 280, which causes the third and fourth clock counters tobe reset to zero. It can be seen that the third and fourth counters, 277and 278 respectively, are second and minute counters respectively, bytracing the circuit from the input from a 60-hertz AC clock to the clockinput of the first counter 275, which also is inputted to the secondcounter 276. Since the first counter 275 is a decade counter, and doesnot reset itself, it has the effect of dividing the input of the60-hertz AC clock by ten and making a 6-hertz input to the clock inputof the second counter 276. We choose to use an output from the Q6 outputof said counter, which gives this counter the effect of additionallydividing by six, making the Q6 output a 1-hertz output. This output issupplied to the clock input of the third counter 277, which will bedescribed later, and every time the Q6 output passes through the firstclock OR gate 279, the first and second counters, 275 and 276respectively, are reset.

The Q6 output is used for many purposes in our circuit. It is suppliedto an input of the first NAND gate 286 which, every time it receives asignal from the Q output of the cycle latch 281, enables the clock to bepassed to the counters 270. Since the cycle latch output has previouslybeen inputted to the other side of the first NAND gate 286, such asignal being the pretest enable signal, this allows the pretest clocksignal to be supplied to the countes 270.

Also, the Q6 output of the second clock counter 276 is then supplied tothe clock select circuit 269. This clock signal is applied to the oneinput of the second clock select NOR gate 291 causing an output to besupplied to the OR gate 292 which, in turn, causes an output to besupplied to the second NAND gate 287, and causes the output from the ORgate 292 to be supplied as an input to the second NAND gate 287. Thetest latch 282, at this time will enable the output of the test clocksignal to the counter 271 in the test circuit 266.

As previously mentioned, the Q6 output of the second counter was a1-hertz output. That output, as can be seen, is also supplied to theclock input of the third clock counter 277, which is a further decadecounter, which divides by ten and supplies that output to the input ofthe fourth clock counter 278. By again taking a Q6 output from thecounter, we have effectively divided the 1-hertz clock signal by anadditional factor of sixty, to have a 1/60-hertz signal, or one-minutesignal, which is supplied both to the input of the second clock OR gate280 to reset the third and fourth clock counters 277 and 278respectively, and also to the input of the first clock select NOR gate290.

The signal to the first clock select NOR gate 290, which arrives everyminute, causes an output from the NOR gate at like intervals which isthen supplied, as before, to the second NAND gate 287, which has beenpreviously enabled, and thus causes the gate 287 to put out the testclock signal at one-minute intervals rather than one-second intervals.

It must be understood that the first clock select OR gate 292, and thefirst and second clock select NOR gates, 290 and 291 respectively, areenabled, or disabled, by the inputs from the test time unit selectswitch 247. For example, if the seconds line is always allowed to behigh, and the minutes line is kept continuously low, only the firstclock select NOR gate 290 will be enabled to pass signals through it tothe OR gate 292, and in this fashion you have selected the minutes unit.If the situation is reversed, and the minutes line is kept high, theseconds line will be kept low, enabling the second clock select NOR gate291 to provide the signal to the OR gate 292, and thus you will haveselected a signal every second to the pretest as the test clock signal.

It therefore can be seen that the test clock signal, if it is inseconds, and the unit thumbwheel switch 246B is set at five, forexample, will cause, in a manner well known in the art, the counter 271to count five test clock signals before supplying the end test signal tothe rest of the system. Similarly, if the minutes unit is selected, thetest clock signal will arrive every minute, and if the unit thumbwheelswitch 246 is set at five, the end test signal will not be supplied forfive minutes. Thus, the operator is enabled to very carefully select thepretest and the test time and control them by means of the scale cyclecontrol, the clock select circuit, and the clock circuits, 269, 265 and268 respectively.

Having now selected the test time, the operator must turn his attentionto the operation of the weigh scale to accurately measure the flow forthe test time. As previously discussed, ours is a dynamic system. Themeans to control the scale, as described in FIGS. 10, 22A and 22B,include a pulse encoder circuit operatively connected to a power supplycircuit 258. The power supply circuit 258 supplies power to the encoder260, the linear vertical displacement transformer (LVDT) 261 and thepoise control circuit 263. Operatively connected to the poise controlcircuit is the poise motor 262.

Now referring to FIGS. 22A and 22B, it can be seen that there is firstprovided a power supply circuit 258. It should be noted that a portionof the power supply circuit labeled 258A, and a portion of the pulseencoder circuit 259A are mounted in the stationary portion of the airgap transformer as indicated in FIG. 22A, while the remaining portion ofthe power supply circuit 258B, the remaining portion of the pulseencoder circuit 259B, as well as the poise control circuit 263 aremounted on the rotatable portion of the air gap transformer as shown inFIG. 22B.

To now understand the operation of the power supply circuit 258, it canbe seen that system common and a positive 12-volt power are brought tothe power supply circuit as shown in FIG. 22A. Since we desire to use anair gap transformer to supply power to the components mounted on thescale, such as the drive motor and the encoder, etc., to eliminatefriction which is present in previous measuring scales due to electricalconnections, etc., we must transform the 12-volt power supply in oursystem to an alternating current. We do this by using a known invertercircuit connected in the manner shown in FIG. 22A, consisting of a firstvoltage divider resistor 295 and a second voltage divider resistor 296connected in series between system common and the system voltage.

Also in the inverter circuit as shown, is a frequency determiningcapacitor 299, positive and negative feedback resistors, 297 and 298respectively, together with an oscillator operational amplifier 300, apositive driver operational amplifier 301, and a negative driveroperational amplifier 302. The outputs of the amplifiers 301 and 302are, in turn, connected as shown to a first pull-up resistor 303 and asecond pull-up resistor 304 and, in turn, to a positive switchingtransistor 305 and a negative switching transistor 306 which have theircollectors connected to the primary coil 307 of the air gap transformerat 307A and 307B respectively. A third pull-up resistor 308 is alsoconnected as shown.

Now to describe the portion of the air gap transformer which is mountedto the scale as shown in FIG. 37, there are shown the secondary coil 309of the air gap transformer. On the rotatable portion of the air gaptransformer 310 is mounted the portion of the power supply circuitlabeled 258B, which consists of a positive secondary coil 309A and anegative secondary coil 309B connected as shown. The positive secondarycoil 309A is connected in a known manner to the positive rectifier 311,while the negative secondary coil 309B is connected to the negativerectifier 312.

In the known manner, these rectifiers are, in turn, connected to theplus 5-volt regulator, the plus 15-volt regulator and the minus 15-voltregulator 314, 315 and 316 respectively (FIG. 22B), which provide poweroutputs to the scale components of plus 5, plus 15, and minus 15 voltsrespectively. It should be understood that the air gap transformer 310just described is one of three air gap transformers on the scale, andtwo additional air gap transformers identified as a second air gaptransformer and a third air gap transformer, 342 and 344 respectively,are in the pulse encoder circuit 259. This circuit is also known fromprevious weigh scales built by Applicants' assignee.

Having now brought power to the scale components, we use the plus 15 andminus 15-volt signal sources to energize the LVDT 261 which will producea signal indicating the linear displacement of the scale. This signal,which is used to control the speed of the poise motor to keep the scalein balance, is supplied to the poise control circuit which is novel andan improvement over Applicants' previous poise control circuits.

The signal from the linear voltage displacement transformer 261 entersthe poise control circuit through the first signal conditioning inputresistor 323, and then travels to the inputs of the signal conditioningoperational amplifier 324 and integrating capacitor 326. The output ofthe integrating capacitor 326 and the signal conditioner feedbackresistor 325 are connected together and the signal therefrom issupplied, both to the output of the signal conditioning operationalamplifier 324, and to one side of the calbrating switch 327. The outputof the signal conditioning operational amplifier 324 is connectedthrough a driver input resistor 331 to the negative input of the driveroperational amplifier 332.

Returning to the calibrating switch 327 just discussed, connected to theother side of the calibrating switch 327 is a first calibrating inputresistor 328. Connected in parallel between the first calibrating inputresistor 328, and the negative input of the driver amplifier operational332, are a second calibrating input resistor 329, and the ratedetermining capacitor 330.

The output of the driver operational amplifier is connected to the baseof a positive follower Darlington transistor, as well as to the base ofnegative follower Darlington transistor, 336 and 337 respectively, aswell as to the input of a crossover capacitor 335. The emitters of thepositive follower Darlington transistor 336, and the negative followerDarlington transistor 337, are tied together and are connected to theoutput of the crossover capacitor 335.

The collector of the positive follower Darlington transistor is hookedto the plus 15-volt power available in the system, while the collectorof the negative follower Darlington transistor is connected to a minus15-volt potential. The emitters of the transistors 336 and 337, whichwere previously discussed are, in turn, connected to the poise motor 262with the other connection to the poise motor being connected to thepower supply. Thus, current is now being supplied to the poise motor andit is ready for operation.

However, two additional components of the poise control circuit whichcontribute to making it novel and an advance over Applicants' assignee'sprevious poise control circuit must still be discussed. These involvethe driver feedback resistor 333 and the driver integrating capacitor334 which are in parallel and connected between the emitters of theDarlington transistors 336 and 337, and the negative input of the driveroperational amplifier 332.

Applicants have found in their previous poise control circuits twoserious and opposite problems in attempting to dynamically weigh fuelwhile it is being introduced into a flow bucket on a weigh scale.

In the run mode, at very low flows, where you have fuel literallydripping into a bucket or, even worse, dripping slowly one drop at atime into a bucket, with Applicants' previous poise control circuit, thesignal supplied by the linear variable displacement transformer 261 tothe circuit would reflect this dripping type of flow even with theprovision of the dash pot 338, and Applicants' felt that some type ofintegrator circuitry with a very low gain would be desirable to overcomethis problem.

However, these are just the opposite requirements which are needed whenone is to calibrate the scale by placing a dead weight in one of theweigh pans, and in such calibration it is desired to have the poiseweight go quickly to one position and stop. If one attempts to calibratewith low gain and high integration, there will be such a time lag thatthe signal from the linear vertical displacement transformer will notget through the integrator circuitry in time to make the appropriatecorrection signal to the poise motor, and you will end up with a serioushunting condition in which the poise weight never stops.

Overcoming these mutually opposite problems provided a serious challengeto Applicants until their novel circuitry was discovered. Applicantsfelt that since the weigh scale operates in the run mode for a greatpercentage of the time, the circuitry that they build should have lowgain with high integration and, indeed, it can be seen that the novelpoise control circuit has a two-stage integrator function built in, buthow to make this run in a calibrate mode reliably alluded Applicantsuntil they came up with the idea of add on circuitry which would bypasssuch circuitry when required.

Applicants knew that they had to add gain without affecting thereliability of the integrator circuit, and had to subtract theintegrator function, again without affecting reliability. Applicantsfinally achieved this by placing the calibrate switch 327, the firstcalibrate input resistor 328, and the second calibrate input resistor329 in parallel with the driver input resistor 331 so that, when thecalibrate switch was closed, and, in effect, two resistances were put inparallel, this had the effect of giving a DC gain boost because theresistance in effect was lowered between the two operational amplifiers324 and 332.

To achieve this effect simultaneously with converting the system to alow integration system, Applicants added a derivative effect to thecircuitry, which is the inverse of the integrator effect, by placing therate determinant capacitor 330 in parallel with the second calibrateinput resistor 329. Thus, when the calibrate switch 327 is in its closedposition, the circuitry has high gain with low integration for use inthe calibrate mode, while when the calibrate switch is open thereliability of the circuitry which was carefully designed to provide lowgain and high integration for the run mode at very low flows ispreserved. Thus, Applicants have solved a long standing problem in theart as to how to dynamically measure low flows in a weigh scale in quickand accurate manner.

The remaining circuit which must be described to complete thedescription of the circuits related to the operation of the scale is theknown pulse encoder circuit 259. As was previously discussed, power hasbeen supplied to the encoder 260 which is mounted on the weigh scale atthe opposite end thereof from the poise motor 262. The encoder outputsignals are supplied in the manner shown, and are connected one each toan up pulse follower transistor 339 and a down pulse follower transistor340. The emitter of the up pulse follower transistor is connected to theprimary coil 341 of the second air gap transformer 342, while theemitter of the down pulse follower transistor is connected to theprimary coil 343 of the third air gap transformer 344.

Mounted to the stationary portion of the air gap transformer 344 is thesecondary coil 345. The secondary coil of the second air gap transformeris indicated by the numeral 346 and this coil is connected through theup base resistor 347 to the base of the up inverter transistor 349,while the secondary coil 345 of the third air gap transformer 344 isconnected through the down base resistor 348 to the base of the downinverter transistor 350.

The emitters of both the up inverter transistor and the down invertertransistor, 349 and 350 respectively, are connected to the systemcommon. The collector of the up inverter transistor 349 is connectedthrough an up pull-up resistor 351 with the 5-volt regulator 294 in thepower supply circuit.

The collector of the down inverter transistor 350 is connected throughthe down pull-up resistor 352 with the same terminal on the 5-voltregulator 294. The collector of the up inverter transistor 349 is alsoconnected to the input of the up count pulser 353, while the collectorof the down inverter transistor is also connected to the input of thedown count pulser 354.

The output of the up count pulser 353, in turn, is connected to the baseof the up output follower transistor 359, while the output of the downcount pulser 354 is connected to the emitter of the down output followertransistor 360. The base of the up output follower transistor 359 isconnected to system common through the up emitter resistor 361, whilethe emitter of the down output follower transistor 360 is connected tosystem common through the down emitter resistor 362.

A major portion of the pulse encoder circuit past the air gaptransformer itself has the function of improving the countability of theencoder pulses. Since the gap of the air gap transformers 342 and 344can vary during operation, and the device is variable in other ways, thepulses coming from those secondary coils 345 and 346 can vary incharacteristics from the pulses present at the primary coils 341 and 343and make countability difficult and thus effect the accuracy of thesystem.

By supplying the pulses to the count pulsers 353 and 354, the pulses areamplified, stretched out and made more uniform to make for easiercountability when they are supplied through the up count output and thedown count output to the time weight display circuit 264 which is morefully described in FIG. 35.

We have now explained the circuitry involved with the air gaptransformer, and to now show how the air gap transformer is physicallymounted to the weigh scale, one may refer to FIG. 43 for a more detailedillustration of the complete air gap transformer, generally designatedby the numeral 575, and the mounting thereof.

It can be seen that the axis of the air gap transformer 575 must bemounted on the center line of the primary fulcrum of the weigh scale.The transformer itself consists of a stationary portion 575A fixed tothe scale base 600, and a movable portion 575B fixed to the upper scalebeam 596.

As described, interposed between the rotatable portion of thetransformer 575B and the upper scale beam 596 are several printedcircuit boards containing on various portions thereof parts of circuits259B, 263 and 258B which are portions of the time weight scale controland timing circuit 250.

Mounted on the stationary portion of the air gap transformer 575A arethe primary coils 307A and 307B from the power supply circuit, thesecond coil of the third air gap transformer 345 and the second coil ofthe second air gap transformer 346.

Mounted on the rotatable portion 575B of the transformer are the primarycoil of the third air gap transformer 343, the second coil of theprimary coil 341 and the positive secondary coil 309A and the negativesecondary coil 309B of the power supply circuit.

Although air gap transformers are old in the art, we found nonesatisfactory for our purpose of using with weigh scales, and had tomanufacture our own transformer using standard available commercialparts. Even though the scale has been known in the art, to enable one topractice the invention easily, some description thereof is offeredthereon, primarily dealing with the winding of the primary coils aboutthe cores necessary to make the transformer operate.

In regard to the primary and secondary coils of the power supplycircuit, the core is what is known as a "ferroxcube" No. 3622 materialwith the primary coils 307A and 307B being wound with 50 turns of No.24AWG wire in a bifilar wound pattern which, in effect, gives you acenter tapped primary coil. The second coils 309A and 309B are eachwound with 120 turns of No. 20AWG wire in a bifilar wound pattern which,in this case, gives you isolated secondary coils.

In regard to the primary coils 345 and 346 of the pulse encoder circuit,these are made of a ferroxcube No. 1408 material and both the primarywindings 345 and 346 and the secondary windings 341 and 343 are madewith 100 turns of a No. 34AWG wire. It is believed that no furtherdescription of the air gap transformer 575 is needed since thisparticular rotary transformer has been known to the art and, inaddition, numerous texts and manufacturers' instructions are availableto one skilled in the art.

A more detailed illustration of the time weight display circuit 264 isshown in FIG. 35. We can see that the time weight display circuitconsists of a decimal select circuit 620 receiving a select signals suchas the high-low select and the pounds/grams select signals as chosen bythe operator. The decimal select circuit 260 outputs a signal to the6-1/2 digit display decoder and driver circuit 621.

The select signals just mentioned are also supplied to a scaling circuit623. A reset signal is supplied to the seven decade BCD counter circuit622 which also receives the output of the scaling circuit 623.

A clock signal is suplied to the input circuit 624 and the output ofinput circuit 624 forms the second input to scaling circuit 623. All ofthis has the effect of providing a signal from the seven decade BCDcounter 622 to the 6-1/2 digit display decoder and driver circuit 621,which it will be recalled is receiving an input from the decimal selectcircuit 620, and causing an output to go from this circuit to the timeweight display 241. A more detailed description of the block diagrams ofFIG. 35 can be obtained by referring to FIGS. 36A and 36B.

The purpose of the decimal select circuit 620 is to place the decimalpoint in the correct position in the time weight display 241 dependingon whether the pounds or grams input are selected from the pounds/gramsswitch 244, or the high and low flow through the injectors is selectedby the high-low select switch 197. Based on these selections, you couldhave four possible positions of the decimal point on the meter. This isbecause you can have four different combinations of flow. You can havepounds of flow in low or or high flow, and grams of flow in low flow orhigh flow.

To illustrate the outputs occurring, let us first assume that we havesignals coming in on the pounds and low flow lines, which would supplyan input to one input of the first decimal select NAND gate 625 and toone input of the second decimal select NAND gate 626. The output of thefirst and second decimal select NAND gates respectively are supplied tothe input of the first and second decimal select inverters, 629 and 630respectively.

The output of the first and second decimal select inverters is in eachcase outputted. The output of the first decimal select inverter 629 goesto the input of the most significant digit 633, while the output fromthe second decimal select NAND gate 626 goes through the second decimalselect inverter 630 to the second most significant digit 634.

Since we must, of course, have along with the indication of pounds a lowor high indication, let us assume now that we have a low indication,which will cause an input into the third decimal select NAND gate 627.Since there is not an input from the grams input to the third decimalselect NAND gate 627, there will be no outputs from that AND gate, butthere will be now the second input, because of the low signal, to thefirst decimal select NAND gate 625 which will be passed through thefirst decimal select inverter 629 to the most significant digit whichwill now light a decimal point.

It can be seen by tracing the various combinations that, for having thepounds and high signal, a signal will travel from the second decimalselect NAND gate 626 through the second decimal select inverter 630 tothe second most significant digit 634. Taking the grams low and highexamples, when you have a grams and a low signal, it can be seen that asignal will pass through the third decimal select NAND gate 627 andthrough the third decimal select inverter 631, to the fourth mostsignificant or middle digit 636. Similarly, when a grams and high signalis present, an output will be forthcoming from the fourth decimal selectNAND gate 628 through the fourth decimal select inverter to the fifthmost significant digit 637.

It can be seen that in the present embodiment of our invention, wechoose not to use decimal points associated with the third mostsignificant digit 635 and the sixth and seventh most significant digits638 and 639 respectively.

As just described, the pounds and grams signals also are supplied to oneinput of the scaling circuit 623 and are supplied one each to the inputof the first scaling circuit AND gate 640 (FIG. 36B) and the secondscaling circuit AND gate 641. At the same time the grams and poundssignals are being supplied to the first scaling circuit AND gate 640 andthe second scaling circuit AND gate 641, the up and down clock signalsfrom the pulse encoder 97 are being supplied to the first input latch643 and the second input latch 644. The Q bar output from the first andsecond input latches is being supplied is connected to the inputs of thetwo input NOR gates 645 and to the count polarity latch 646.

Depending on whether grams or pounds are selected, the output of the twoinput NOR gate 645 is supplied to each of three identical ratemultipliers 647, and also to the second input of the second scalingcircuit AND gate 641, which, if a pound signal is being supplied, willcause an output to occur from the scaling circuit OR gate 642 andprovide an input to both the up NAND gate 648 and the down NAND gate649, and depending on which of the first input latch or second inputlatches are supplying the signal to the count polarity latch, the otherinput to the up NAND gate 648 or the down NAND gate 649 will be providedwhich is necessary to provide the proper signals to the counter circuit622.

It should be noted that in the case where the grams signal is beingsupplied to the first scaling circuit AND gate 640, the grams conversionfactor of four, five and four are set into the rate multipliers 647,which will cause the correct count to be transmitted through the firstscaling circuit AND gate 640 and the scaling circuit AND gate 641 andscaling circuit OR gate 642 to the inputs of the up NAND gate 648 andthe down NAND gate 649.

Here again, depending on whether the first input latch 643 or secondinput latch 644 is supplying a signal to the count polarity latch 646,either the up NAND gate 648 or the down NAND gate 649 will receive thesecond input which it needs to provide an output through the countercircuit 622.

To now describe the counter circuit in more detail, it can be seen thatthis circuit receives a manual reset signal from the auto manual switch363 and an auto reset signal from the float detection control circuit381. This signal comes into a reset OR gate 650. It is to be noted thatit does not matter which of these signals is being supplied, as it longas either signal is being supplied, an output will be provided from thereset OR gate to each of the seven BCD counters in the seven decade BCDcounter circuit 622. Providing that neither the auto reset or manualreset signals is causing an output from the reset OR gate 650, thecounters will immediately start counting up or down upon receipt of anup or down signal from the scaling circuit 623 and this will continueuntil either the auto reset or manual reset signal is received by thereset OR gate 650 which will immediately, but momentarily, cause all thecounters to be reset to zero. Each of the decade counters 651 in theseven decade BCD counter circuits are connected to a correspondingdecoder driver 652 in the 6-1/2 digit display decoder and drivercircuit, except the most significant counter 651A, which is connecteddirectly to a transistor driver circuit 623, well known in the art.

The decoder drivers 652, upon receiving signals from the decadecounters, provide the appropriate seven segment code to the appropriatedigits 633-639 respectively. In turn, the signals from the significantdigits 633-639 provide the necessary signal to the time weight display241 to illuminate the same, and provide the system operator with anaccurate an instantaneous indication of the weight present in the weighscale at any time.

Now that we have seen how the weigh scale in our system dynamicallyweighs fuel as it is placed on the scale to eliminate the problems longstanding in the art due to scale friction, and the errors due to staticweight and fuel drip effects at low flows, we shall now describe how thesignals coming from the weigh scale are utilized to display the weightof fluid in the scale at any given time.

Referring now to FIG. 11, the electronics necessary to operate thedetection subsystem of the present invention and, more particularly, thefloat detection system, are shown in block diagram form in FIG. 11. Aspreviously discussed, it is necessary, during a flow meter calibration,to eliminate the need for an operator to keep the float at an accuratelevel by the use of his eyes to gauge the movement of the float.

As it has been shown, the float can fluctuate enough to greatly effectthe accuracy of the calibration without the operator even being aware ofit, or being able to correct it satisfactorily. We have, therefore,provided an electromechanical means of detecting and monitoring theposition of the float in the flow tube as depicted in the float detectorsystem 89A shown in FIG. 5.

It can be seen that the actual device which detects and keeps track ofthe float consists of an infrared transmitter 100 and, a pair of dualphoto receivers generally designated by the numeral 99 and including ahigh receiver 99A and a low receiver 99B. The transmitter and receiverare movable up and down the length of the flow tube by moving up anddown as part of a float follower apparatus 93 on the ball screw 96,which is rotated by the stepping motor 95 in response to signalsreceived from the high receiver 99A and the low receiver 99B.

Since the operator of our improved system must set up the floatdetection system before beginning flow into the weigh scale previouslydescribed, he is provided with a series of switches to perform thisfunction, which operates through the float detector circuit. One set ofthese switches is provided on the control panel of FIG. 4 and theseswitches consist of a fast down switch 377, a fast up switch 376, a slowdown switch 375, a slow up switch 374, a jog down switch 373 and a jogup switch 372. These switches operate through the float detector controlcircuit 381 to control the movement of the float follower 93 previouslydescribed.

A second set of identical switches are intended for remote use, and areillustrated at the bottom of FIG. 11, and are placed on the calibrationapparatus 58 on the control panel 395 thereof. In this case, the fastdown, fast up, slow down, slow up, jog down and jog up switches arenumbered 393-388 respectively.

The operator will switch the system on by depressing the on-off switch364 and will first select the manual mode of operation on the modeselect switch 363. If necessary, he will test out the segment of thefloat detector position display 367 by pushing the light test switch 366and reset it with the reset switch 365 before operating the manualbutton.

To set up the float detector subsystem 89A for use, the operator willmake certain that the float 101 in the glass tube flow meter 78 is aboveor below the reference line on the glass tube 159. He will then causethe float follower 93 to be positioned between the reference mark 159and the float 101 by use of the button just described. When the float isso positioned, the operator will depress the auto enable switch 371which will cause the float follower 93 to automatically seek the float,and push the auto start switch 371 which, because the circuitry assumesthat the float is always below the float follower 93, will cause thefloat follower to proceed in a downward direction, which it willcontinue to do until it detects the reference line 158.

At this point, the float detector control circuit will automaticallycause the float detector position display 367 to assume a zero readingbecause of the operation of the float detector display circuit 379.

The float detector position display is enabled to display the positionof the float because of the operation of the other circuits shown onFIG. 11. The LED transmitter 100 transmitting infrared light to the highreceiver 99A and the lower receiver 99B across the float will give anindication of whether the float is high, low or in-band, and the testwill continue to proceed as long as the float is in-band.

The receiver sends a signal to the optical conditioner circuit. Theoptical conditioner circuit 384 provides power to the transmitter 100,as well as receive signals from the receiver 99, and amplifies anddecodes the signals into high, low and in-band signals, and suppliesthem to the float detector control circuit 381 for the purposespreviously described.

To move the float follower 93 having the transmitter 100 and receivers99A and 99B, a driver circuit 383 receives signals from the floatdetector control circuit when it is necessary to move the float followerand this, in turn, supplies the proper signals to the stepper motor 95,which causes the float follower to move up or down.

To accurately determine the location of the follower with respect to thereference point, which as previously discussed must be very accuratelydone, as this will be used to make the flow meter scale, the positionpulse encoder 97 sends precise pulses in regard to its position to thefloat detector control circuit which converts these pulses into adistance from the reference mark and displays the same.

A more detailed illustration of the float detector control circuit 381,the optical conditioner circuit 384, the driver circuit 383, thetransmitter 100 and receiver 99 can be obtained by referring to FIGS.27B, 28, 29, 30, 31, 32, 33A, 33B, 33C, 34A, 34B and 34C. Such moredetailed circuits also include the travel limit circuit illustrated inFIG. 11 which prevents the float follower 93 from extreme travel eitherup or down, which may bring it to the end of the ball screw 96 and causedamage to the apparatus.

Referring now to FIG. 7, the switches previously described which theoperator uses to set up the float detection system and begin itsautomatic operation such as the mode select switch 363 and the autoenable switch 371, the fast down, fast up, slow down, slow up, job downand job up switches, 377, 376, 375, 374, 373 and 372 respectively, allinput to the manual select and switch input circuit 396 within the floatdetector control circuit 381.

Depending on the switch the operator has pushed, for example, if he haspushed the fast up switch 376, the manual select and switch inputcircuit sends a signal to the clock speed select circuit 397 and thedirection polarity latch circuit 399. Since we have assumed the operatorhas pushed a fast up switch 376, the direction polarity latch circuitwill be latched in the up position.

While this is occurring, the clock speed select circuit 397 iscontinually receiving slow and fast signals from the clock circuit 398.Again, depending on which button is pushed, one of the signals will bepassed through the clock speed select circuit to the travel limitcircuit 386. The function of the travel limit circuit is to merelyinhibit travel in a direction when a travel limit for that direction hasbeen reached.

When a travel limit has been reached for a certain direction, the travellimit circuit discontinues passing the signals it receives from theclock speed select circuit 397 through to the stepper motor translatorcircuit 401. Under normal conditions however, when neither of the limitshas been reached, the travel limit circuit 386 merely performs thefunction of passing whatever signals the clock speed select circuitoutputs through to the stepper motor translator circuit 401.

The stepper motor translator circuit's function is to first of allreceive a signal from the direction polarity latch circuit 399 whichwill tell the stepper motor which way to rotate, and then to use thissignal in combination with the clock signal being received from thetravel limit circuit. The stepper motor translator circuit takes thesignals received from the travel limit circuit 386 and directionpolarity latch circuit 399 and produces the specific four phase ofsignals needed to operate the stepper motor 95.

However, before these signals can operate the stepper motor 95, theypass through the stepper driver circuit 383 where they are amplified tothe level necessary to operate the motor. The stepper motor 95, in turn,drives the float detector up or down, again depending on the switchselected by the operator.

While this happening, the turning of the ball screw 96 is, in turn,rotating the pulse encoder 97 which produces pulses, depending on theamount of rotation of the pulse encoder, and sends these pulses to thefloat detector display circuit 379. These pulses are acted upon toproduce a signal to the float detector position display representing theposition of the float detector to produce a readout of the position ofthe flow meter float in relation to the fixed reference mark 158 on theglass flow tube 78.

If the operator has finished the preliminary setup of the system and hasthe float detector on the reference mark 158, the operator will nowchoose to go into the automatic mode of operation after resetting thefloat detector position display 367 to zero by pressing the display testswitch 366.

In order to go into the automatic mode of operation, the operator mustdepress the auto manual switch 363 to the auto position, the auto startswitch 371, and, if he wishes the automatic abort 403 operational, hemust press the FDS abort switch 404. If the switches are set so theseoperations occur, the optical conditioner circuit 384 which is receivingsignals from the float follower 93 will pass through a condition signalto the auto select circuit 402 whose purpose is to indicate whether thefloat is high, low or in-band.

The auto select circuit, as previously discussed, is the circuit thatdetermines whether the float is high, low or in-band. First, assumingthat the float is in-band, the auto select circuit 402 will not supplyany signal to the clock speed select circuit 397, the direction polaritylatch circuit 399, or the auto abort circuit 403.

However, if the auto select circuit determines that the float is high, asignal will be supplied to the clock speed select circuit 397 whichwill, in this case, act to take the fast signals from the clock circuitand pass them through the travel limit circuit, the stepper motortranslator circuit 401, and the stepper driver circuit 383 to thestepper motor 95, to cause the float to move in the upper direction at afast rate of speed. This occurs because the signal from the auto selectcircuit 402 is supplied to the direction polarity latch circuit to latchit in the up position.

The reverse happens if the auto select circuit 402 determines the floatis low. The same signal will be selected and sent to the clock speedselect circuit 397 and the direction polarity latch circuit 399 to causethe float detector to operate in a down direction at a fast speed.

Because the auto select circuit 402 also supplies a signal to the autoabort circuit 403, which is, in effect, the timer circuit, the autoabort circuit using the fast signals from the clock circuit 398, acts asa time base which will accept a certain number of signals before causingan abort to occur, presuming the FDS abort switch 404 is in its closedposition. If it is, a signal will be supplied to the time weight scalecontrol and timing circuit 250 (FIG. 10) to cause the test to abort.

This completes a general description of the float detector controlcircuit, and a more detailed description of each of the circuits withinthis circuit can be had by referring to FIGS. 27A and 27B.

Referring now to FIG. 27A and, more particularly, the manual selectcircuit 396, it can be seen how the signals from the fast up, slow up,fast down, slow down, jog up and jog down switches, 376, 374, 377, 375,372 and 373 respectively, are supplied from the switches to the clockselect circuit 397. Each of the aforementioned switches is connected bysuitable electrical connections to the hex switch debouncer 406, whosepurpose is to condition the switches signal to eliminate any extraneouselectrical signals which may occur when the switch contacts physicallycontacts each other.

Each of the signals from the switches is then passed through one of sixidentical inverters 407, and then by means of the shown connections toan exclusive OR circuit consisting of five exclusive OR gates 408connected in the manner shown. The purpose of the exclusive OR circuitis to provide that a signal will be supplied to the clock select circuitif, and only if, only one of the switches 372-376 is pushed. It can beseen that if one attempts to push two buttons at a time, or one pushesnone of the buttons, no signal will be supplied through the last OR gatewhich, although identical to the other four OR gates of the circuit hasbeen indicated by the numeral 408A. It can now be seen that the operatorsetting of the switches 372-377 does lead to a signal being supplied tothe clock select circuit 397 as just described. It can be seen that atthe same time this is happening, the clock circuit 398 is also supplyingsignals to the clock select circuit 397.

As previously explained, the function of the clock circuit is to providepulses to the clock select circuit and other of the circuits shown inFIG. 7. It does this through a well known oscillator circuit consistingof the two oscillator inverters 410, the oscillator capacitor 411, theoscillator variable resistor 412 and the oscillator resistor 413. Sincethis oscillator circuit is well known in the art, it need not bedescribed further herein. It suffices to say that the output of theoscillator circuit is supplied to the divider circuit 414 which hasthree outputs, those being a Q4 output, a Q5 output and a Q7 output.

It can be seen that the Q4 and Q5 outputs are supplied to the clockselect circuit, while the Q7 output is supplied to the auto abortcircuit, which will be described later.

The signal from the last exclusive OR gate 408A then enters the logicmatrix formed by the plurality of identical AND gates 409A-409H. It canbe seen that the Q4 and Q5 outputs are continuously being supplied toAND gates 409A and 409B which, in turn, then continually output to theAND gates 409C-409F.

Thus, each time one of these AND gates receives a signal from theinverter 407, corresponding to one of the switches 373-376, that ANDgate will provide an input to the eight input OR gate 415. It can beseen that the output of the eight input OR gate 415 is the signal whichis supplied to the travel limit circuit 386 illustrated in FIGS. 27B and7.

We have now described how the fast up, slow up, fast down and slow downswitches, 376, 374, 377 and 375 respectively, provide a signal to thetravel limit circuit. The jog up switch 372 and the jog down switch 373provide a signal in a similar manner. The previously described manualenable signal from the last exclusive OR gate 408A was previouslysupplied to the identical AND gates 409G and 409H.

It can be seen that when the jog up switch is pushed, the signal fromthe corresponding inverter 407 goes to the other input of AND gate 409G,which then produces an output to the eight input OR gate 415, which thenprovides the signal to the travel limit circuit. Similarly, when the jogdown switch 373 is pushed, the corresponding inverter 407 supplies asignal directly to the other input of the AND gate 409H which, in turn,provides a signal to the eight input OR gate 415 and then to the travellimit circuit 386.

It should be noted in connection with the jog up and jog down switches372 and 373 respectively, that when these switches are pushed, there isonly a single instantaneous signal supplied to the travel limit circuit.This is essentially because the corresponding AND gates 409G and 409Hare not being continuously supplied with the clock signal input from theAND gates 409A and 409B, as were the inverters 409C-409F correspondingto the other switches in the circuit.

It is to be noted that there are still AND gates 409I and 409J in theclock select circuit. In a manner to be defined hereinafter, these areeach receiving the fast clock signal from the Q4 output of the clockcircuit previously described, and also have an input from the auto highand auto low signals from the auto select circuit also to be describedbelow.

When the AND gate 409I, for example, receives a signal from the autohigh signal from the auto select circuit, the output of AND gate 409Iwill be supplied to the input of the eight input OR gate 415, and theoutput of the eight input OR 415 then supplies a signal to the travellimit circuit.

Similarly, when the auto low signal is supplied to the input of the ANDgate 409J, the output of said AND gate is supplied to the input of theeight input OR gate 515, which again supplies a signal to the travellimit circuit. This completes the description of the clock selectcircuit 397.

To now more fully explain the auto select circuit, one can refer to theillustration thereof in FIG. 27A, and will notice that the auto high andauto low signals are the signals coming from the optical conditioner 384of FIG. 7. It is to also be noted that the auto start signal and theauto mode signal come from the auto start switch 371 and the auto modeswitch 363 shown on FIG. 4.

Depending on the position of the float follower 93, and thus the signalscoming from the optical conditioner circuit 384, either the auto high,in-band or low signals will be entering the auto select circuit at anygiven time.

As was previously described in setting up the system, the detector hadto be set on the reference line, and the float had to either be above orbelow that reference line before the system can be placed in automaticmode by the operator to calibrate the flow tube at different positionsautomatically. It has already been described how the operator can putthe float either above or below the reference line and set the detectorto the reference line. It will now be described how the system works inthe automatic mode.

As was previously described, the operator, to place it in automaticmode, will select automatic mode on the auto manual select switch 363.Assuming in the first instance that the operator has the float below thereference line, and the float follower 93 must now track and lock ontothe float 101, the operator will momentarily depress the auto startbutton 371 and, as described, the optical conditioner circuit alwaysassumes the float below the reference line, and the auto select circuitwill then cause the float detector 93 to move downward and lock onto thefloat.

In this case, as will be described, a low signal is caused to enter theauto select circuit, which causes the float follower 93 to proceeddownward and find the float. This will be described in more detail inconnection with FIG. 32.

In the second case where the float is above the float detector, which islocked on the reference line 158 on the flow tube 78, when the autostart button 371 is depressed and held, this will cause the floatfollower 93 to rise in relationship to the reference mark as long as thebutton is depressed. Normally, the operator will view the float follower93 and observe it until it rises above the float, release the auto startbutton 371, which allows the float detector to reverse position, andcome down and lock on the float, after which the float detector willtrack the float automatically as the flow is changed through the flowtube by the operator.

This occurs because as long as the button 371 is held, the floatdetector will rise because the signal being supplied from the auto startbutton 371 to the input of the single debounce circuit 419 is suppliedthrough the auto select inverter 416D to the set input of the auto latch420, and to one input of the auto select OR gate 417. The inputting ofthe signal to the auto select OR gate 417 produces an output therefromto the input of one of the auto select AND gates 418, as well as to thehigh transistor 424 through the high base resistor 423.

The collector of the high transistor 424 will cause the high light 368to light. It should be understood that the resistor transistorcombinations in the auto select circuit act as light drivers.

To now return to the auto select AND gate 418A, this is also receivingan input from the Q output of the auto latch 420 as previouslydescribed, as is the input of the other auto select AND gate 418B. Since418A and 418B are also receiving an input from one of the auto selectinverters, depending on which inputs are being received, a signal istransferred to the inputs of one of the clock select AND gates 409I or409J, which, in turn, produce outputs to the eight input OR gate 415which, in turn, supplies a signal to the travel limits circuits to bedescribed.

The low signal being supplied to the system by the optical conditionercircuit, in addition to being supplied to the auto select AND gate 418,is also supplied through the low base resistor 425 to the low transistor426, which causes the low light 370 to light. In addition, that signaltravels to the auto abort circuit 403 and the direction polarity latchcircuit 399.

In the case where the operator wants the float follower 93 to risebecause the float 101 is above it, and is continuously holding down theauto start button 371, in addition to the low signal being continuallysupplied, a high signal will be supplied through the auto selectinverter 416A and the auto select OR gate 417 to the input of the autoselect AND gate 418 to the input of the clock select AND gate 409I, andthen to the input of the eight input AND gate 415. It will also besupplied to the auto abort circuit 403 and the direction polarity latchcircuit 399.

It should be understood that in this case the high signal and the lowsignal will both be present at the direction polarity latch circuit, butsince the high signal is dominant in the direction polarity latchcircuit, whereas the low signal is dominant in the optical conditionercircuit 384, the direction polarity latch circuit will cause the floatfollower 93 to rise, as long as the auto start button 371 is held in.

When the operator has caused the float follower 93 to pass the float101, he will remove pressure from the auto start button 371, which willremove the dominant signal from the direction polarity latch circuit399, allowing the low signal to again become dominant, and cause thefloat detector to move in a downward direction to seek and lock onto thefloat 101.

When the float follower 93 locks onto the float 101, because of thedecoding of the signal from the optical conditioner circuit 384 whichwill be described later, an in-band signal is caused to enter the autoselect circuit, pass through the auto select inverter 416B through thein-band base resistor 421 to the in-band transistor 422. As before, thein-band transistor, in combination with the in-band base resistor, actsas a light driver circuit, and will cause the in-band light 369 tolight.

If the operator is through calibrating a flow meter, or is at any pointin the operation of the system where he desires to go to manual mode, hewill switch the auto manual switch 363 to the manual mode, which willremove the auto mode signal from the auto select circuit and supply amanual mode signal to the reset input of the auto latch 420 to reset theauto select circuit. The same signal will also be supplied to thedirection polarity latch circuit 399 and act as an auto polarity inhibitsignal for purposes to be described.

A relatively slow time base signal is supplied from the Q7 output of thedivider circuit 414 to the auto abort time counter 433. This counterwill be held in its reset mode, as long as neither the high nor lowsignal is being supplied to the auto abort circuit from the auto selectcircuit 402.

At the point where a high or low signal is being supplied to the autoabort circuit 403, because of the actions of the auto abort NOR gate430, a reset signal will be supplied to the auto abort time counter 433.This will cause the Q5 output from the counter to be supplied to oneinput of the abort NAND gate 432, and the same signal which was suppliedto the reset input of the counter 433 will be supplied through the autoabort inverter 431 to the other input of the NAND gate 432.

The NAND gate 432 having two inputs present will then output an abortsignal to the FDS abort switch 404 which, if closed, will cause thatsignal to travel to the time weight scale control and timing circuit 250(see FIGS. 7 and 10).

The circuit that controls the direction of the movement of the floatdetector is the direction polarity latch circuit 399 consisting of thefirst and second two input NOR gates 434A and 434B, together with thefirst and second four input NOR gates 435A and 435B. The signalspreviously supplied to the first and second four input NOR gates 435Aand 435B by the clock select circuit 397 and manual select circuit 396,together with inputs to the four input NOR gates from the first andsecond two input NOR gates 435A and 435B, together with each of the fourinput NOR gates receiving a signal by cross coupling from each other,form the input to these portions of the direction polarity latch circuit399.

The two input NOR gates 434A and 434B receive an input from the manualmode portion of the auto manual select switch 363. The first two inputNOR gate 434A also receives an input from the auto low signal in theauto select circuit 402. The second two input NOR gate 434B likewisereceives a signal from the auto high signal from the auto select circuit402. The output of the second four input NOR gate 435B is then suppliedto the travel limit circuit 386 and to the stepper motor translatorcircuit 401.

It will be recalled that the purpose of the travel limit circuit was toprevent damage to the float detection system due to excessive travel ineither direction by the float follower 93. THe travel limit circuit, aspreviously described, receives signals from the direction polarity latchcircuit 399 and the clock select circuit 397. In addition, signals arereceived from the travel limit switches 387 (FIG. 11).

Normally, you will not be receiving either the high limit or the lowlimit signals 387 because the float detector will not have reachedeither of the preset limits. This will result in off signals beingsupplied to both the first travel limit inverter 436A and the secondtravel limit inverter 436B. This, in turn, because of the action of theinverters, results in on, or high, signals being supplied to one inputeach of the first travel limit OR gate 437A and the second travel limitOR gate 437B. Because of the nature of the OR gates, they will bothoutput to the inputs of the first travel limit and gate 438 which willprovide one of the inputs to the second travel limit AND gate 438Aenabling the clock signal to be passed through the second travel limitAND gate to the stepper motor translator circuit 401 enabling thestepper motor to be operated.

However, as soon as a low limit or high limit signal is supplied, thesituation changes. For purposes of illustration, let us presume that onsignal is received from the low limit switch portion of the travel limitswitches 387. This will then result in an off signal being supplied fromthe second travel limit inverter 436B to one of the inputs of the secondtravel limit OR gate 437B.

Assuming at this point that the direction polarity latch circuit 399 iscausing the stepper motor to travel in a down direction, you will haveneither input to the second travel limit OR gate 437B. Even though youare still getting an output from the first travel limit OR gate 437A tothe input which, in turn, causes one input to go to the first travellimit AND gate 438A, since the second input is not present there will beno output to the second travel limit AND gate which will not enable theclock signal to travel to the stepper motor translator circuit 401causing the stepper motor to stop.

Presuming that the float detector 93 has been caused to reach its lowlimit by excessive downward travel of the float, at this point theoperator must either change the flow through the flow meter 78 to causethe float to go up, and thus the float follower to follow it if we areto leave the system in the auto mode, or he must go into the manual modeand take the necessary actions to cause the float detector 93 to travelin the opposite direction.

When the operator does this, he will change the polarity of the signalbeing received from the direction polarity latch circuit. This willcause the input to the second travel limit OR gate 437B from thedirection polarity latch signal to go to its high condition, this,because of the input coming from the first travel limit OR gate beinghigh and the output now coming from the second travel limit OR gatebeing high, will cause an output to come from the first travel in theAND gate into the second travel limit AND gate once again enabling theclock signal to be passed through to a stepper motor translator circuit401.

Similarly, if the high limit signal is being supplied to the input ofthe first travel limit inverter 436A from the high limit portion of thetravel limit switches 387, this will cause a low signal to be outputtedto the input of the first travel limit OR gate 437A. Similarly to whathappens before, the high signal coming from the direction polarity latchis inverted by the third travel limit inverter 436C causing two lowsignals to be present at the inputs of the first travel limit OR gate437A.

Similarly to that just described, this prohibits the clock signal frompassing through to the stepper motor translator circuit 401. Again, theoperator must take the appropriate action to receive the travel andenable the stepper motor to operate again.

In order to drive the stepper motor 95, it is necessary to have astepper motor driver circuit and a stepper motor translator circuit 401.The stepper motor translator circuit has already been described asreceiving the clock signal from the travel limit circuit 386, and thepolarity signal from the direction polarity latch circuit 399, thesesignals are received by the clock and up down inputs of the binarycounter 440.

These signals are converted with the aid of the stepper motor translatorexclusive OR gate 441, and the first and second stepper motor translatorinverters 442A and 442B into the standard four-step four-phase sequenceneeded by stepper motor translator circuits known in the art. While wehave chosen to build our own stepper motor translator circuit 401, itshould be understood that this circuit may be replaced by one well knownin the art, such as one manufactured by the Superior Electric Co. areknown as STM 1800, and our invention will work equally as well.

To continue with a description of our stepper motor translator circuit401, it can be seen that there are four identical output circuitsconsisting each of a stepper motor translator inverter 442, a steppermotor translator output base resistor 443, a stepper motor translatoroutput transistor 445 and a stepper motor translator pull-up resistor446 to carry the four phases of signals necessary to drive the steppermotor to the stepper motor driver circuit 383. For purposes ofillustration, we have numbered the first through fourth stepper motortranslator circuits 442C-442F respectively, while we have numbered eachof the stepper motor translator output base resistors 443A-443Drespectively. Similarly, each of the four stepper motor translatoroutput transistors have been labeled 445A-445D respectively, while eachof the four stepper motor translator pull-up resistor has been labeled446A-446D respectively.

A detailed description of the stepper driver circuit 383 is given inFIG. 26. It can be seen that the phase one, phase two, phase three andphase four signals being supplied by the stepper motor translatorcircuit 401, previously described, are being inputted to the drivercircuit into corresponding Darlington transistors.

The phase one signal will be supplied to the first stepper motor drivertransistor 448, the phase two signal will be supplied to the secondstepper motor driver transistor 449, the third stepper motor drivertransistor will receive the phase three signal, while the fourth steppermotor driver transistor will receive the phase four signal.

It is to be understood that the first, second, third and fourth steppermotor driver transistors 448-451 respectively, are identical Darlingtontransistors and may be such as Motorola Model No. MJ3000 manufactured byMotorola Semiconductor Products. Although not numbered, each of thestepper motor driver transistors include an identical diode asillustrated as part of the product. It is not felt that additionalcircuit description need be given on these items, since they arestandard commercially available items.

The output from the selector of the transistors is then supplied to thestepper motor. For example, the emitter of the first stepper motordriver transistor 448 would supply a phase one output to the steppermotor 95 and similarly, the output of the second stepper motor drivertransistor 449 would supply a phase two output to the stepper motor.Likewise, the third and fourth phase outputs are supplied by the outputsof the third and fourth stepper motor driver transistors 450 and 451respectively, thus supplying the standard input to the stepper motor 95needed by the well known commercial devices. The stepper motor has ampleinstructions with it for use by one skilled in the art, and may be suchas Model No. MX111F012 manufactured by the Superior Electric Company.

To complete the description of the stepper motor driver circuit, it isto be noted that the stepper motor current limiting resistor 452 isplaced in series between the stepper motor common and the power supply.

To understand how the float 101 is tracked, it is necessary to have adetailed description of the optical conditioner circuit 384. A detailedillustration of the optical conditioner circuit can be had by referringto FIGS. 32, 33, 33A, 33B and FIG. 33C.

A block diagram of the optical conditioner circuitry 384 is shown inFIG. 32. It can be seen that this circuit consists of a power supply461, a decode circuit 463, an amplifier circuit 460 connected to saidpower and said decode circuit, and a synchronous modulator 462 connectedto the power supply and the decode circuits.

A detailed illustration of the amplifier circuit 460 is shown in FIG.33A. Power comes into the power supply (FIG. 33C) between ground and aplus 15-volt source present in the system.

A first input filter capacitor 465 is connected across these terminalsfor filtering purposes. The power supply voltage regulator 467 is athree terminal regulator having an input, a common and an output, withthe input connected to the plus 15-volt source, the common connected tosystem common and the output being used for providing a 8-volt sourceacross the regulated source across which the first output filtercapacitor 468 is connected. This supplies the power for the amplifiercircuit 460, the decode circuit 463 and the dual photo receiver 99.

The 8-volt output is then supplied to a power supply limiting resistor466, through which it is supplied to to the second output filtercapacitor 469. From here it is supplied to the synchronous modulatorcircuit 462 and the transmitter circuit 100. Therefore, now all of thecircuits involved in the optical conditioner circuit 384 are suppliedwith power.

To get a high readability of the signal from the transmitter 100 by thereceivers 99, it is desired to have a very bright infrared light outputfrom the transmitter 100. This cannot be obtained by continuouslyrunning the transmitter so, in essence, what one does is flash thelight, rather than run it continuously, and gate the receiver so that itwill attempt to read the light at the same time it is flashing. It isthe purpose of the synchronous modulator circuit to flash thetransmitter and gate the receiver. It does this by accepting power fromthe power supply circuit 461 and feeding it to the oscillator circuit471 of the synchronous modulator 462. The oscillator circuit 471, inturn, supplies an output to the modulator current limiting resistor 472which acts as the LED enable signal which will cause the LED to flash ina manner to be described.

As already stated it was necessary to produce a relatively intense beamof light which would pass through the flowmeter tube and would bereceived by two optical receivers (photo transistors 495A and 495B inthis particular design). Obscuration of this beam of light by the float101 would be detected by these receivers, and would be an indication ofthe position of the float.

If the float position is to be determined to high accuracy, the beam oflight between transmitter 100 and receivers 99A and 99B must be of verysmall dimension in the direction of float motion (vertical). On theother hand, to achieve a large signal it is desired to have a largeoptical aperture. These two requirements conflict. As a furtherconflicting factor there must be two such beams, one for each receiver,and these two beams while being very thin (approximately 0.010 inches insome cases) must be spaced very closely together, for this spacingdetermines the "in band" or dead zone dimension which may be as small as0.004 inches.

If conventional optics were used to form two closely spaced, very thinbeams the optical system would be so large that it could not be fittedinto the highly restricted space on the carriage and between theadjacent flow tubes. The solution was to design a novel optical headwhich used fiber to transform the aperture shape from two very thin,closely spaced rectangular elements 99F to two cylindrical elements 99Ethat can serve as inputs to the two photo receivers 495A and 495B.

The optical head 99C (FIGS. 49 and 50) consists of an epoxy block intowhich are molded two bundles 99D of optical fibers. One side of the headis in close proximity to the flow tube and is perpendicular to the lineof sight through the flow tube to the transmitter. The two bundles offiber terminate on this face to form two closely spaced, parallelapertures 99F, each very small vertically and approximately as wide(norizontally) as the diameter of the float. These two apertures arespaced by a few inches (typically 0.004 to 0.010). The fiber opticbundle serves as a means of efficiently coupling optical energy from thetwo narrow apertures to the photo receivers.

On the opposite side of the flow tube from the receiver head, justdescribed, is the transmitter 100. The transmitter consists of a singlelight emitting diode (LED) 453. Its emitting area is relatively large incomparision to the very narrow receiver aperture and consequently it ismasked by a narrow aperture (typically 0.010 inch). This singletransmitter illuminates both receiving apertures.

The output of the oscillator circuit 471 (FIG. 33C) is supplied throughthe output driver coupling capacitor 476 to the base of the synchronousmodulator driver transistor 473. The output from the collector of thesynchronous modulator driver transistor is supplied to one input of theupper receiver latch 478 (FIG. 33B) for purposes to be described. Theemittter of the synchronous modulator transistor driver 473 is connectedto ground, while interposed between the base of the transistor 473 andthe input voltage is a first driver pull-up resistor 474 connected asshown in FIG. 33C, while a second driver pull-up resistor 475 isinterposed between the collector of the synchronous modulator drivertransistor 473 and the power supply.

It should be understood that the oscillator circuit consists of standardwell known components, such as the four identical oscillator capacitors480, the first oscillator resistor 481, the second oscillator resistor482 and the third oscillator resistor 483, as well as the oscillator ICchip which may be the same as Model No. LM556 manufactured by NationalSemiconductor Corporation.

It can be seen that since the actual component values of the variouscomponents of the oscillator circuit are supplied and the actual valuesare given, it is believed that the building of the oscillator circuit471 for the inclusion in the synchronous modulator circuit 462 is wellwithin the skill of the art.

Referring to FIG. 29, there is shown a schematic diagram of the infraredtransmitter 100 which receives the output signal previously mentionedfrom the synchronous modulator, which was the LED enable signal, andinputs that signal to the base of the transmitter transistor 453.

When the signal is received at the base of the transistor 453, thetransistor will turn on the collector circuit and supply a signal to thelight emitting diode 454. Since, as we know, the signals areintermittently received at the base, this will cause the aforementionedflashing of the diode 454, which will be the light source for thereceiver 99 to be described.

The current continues on through the light emitting diode 454 throughthe current limiting resistor 455 to complete the circuit to ground. Atthe same time this is occurring, the emitter, of course, is the sourceof the current which is passed through the collector to the lightemitting diode, and the turn off resistor 457 is supplied to ensure thatwhen there is no signal being supplied to the base of the transistor,there is a complete shut-off of current to the light emitting diode.

The transistor filter capacitor 456 is supplied to filter out anyextraneous signals which may be present in the system. The signal fromthe light emitting diode 454 is transmitted to the receiver circuit 99,which consists of a dual preamp circuit 489 and a dual photo receivercircuit 488.

The photo-transistors 495A and 495B are normally bias slightly on by thecurrent coming through the upper and lower base resistors, 494B and 495Arespectively, but when light is received by such photo transistors, itsis their characteristic to conduct, and the current present at theemitter of such transistors is then passed through the collectorthereof, causing a signal to be sent to the corresponding portion of thedual preamp circuit.

The signal coming into the upper and lower preamp transistors 498B and498A respectively, at the emitter thereof causes the bias thereof todecrease as the strength of the signal increases, and causes an outputthrough the collector thereof. When the bias of the preamp transistorsdecreases, the current decreases, and the voltage of the collectorrises, thus sending a signal out of the dual preamp circuit to theamplifier circuit, amplifying the output of the photo transistors asdesired.

As is well known in the art, the lower and upper collector pull-upresistors 502A and 502B, and lower and upper first base bias resistors499A and 499B, together with the lower and upper second base biasresistors 500A and 500B with the lower and upper base bypass capacitors501A and 501B form bias networks, placing the initial bias on the preamptransistors 498A and 498B.

Referring to FIG. 33A, we can now describe the amplifier circuit. Thereceiver circuit power supply resistor sends power to the dual receivercircuit 99 and, in turn, receives back the lower and upper signals fromthe dual preamp circuit 489.

These signals come into the dual input circuit 497 by way of the lowerfirst input coupling capacitor 507 and the upper first input couplingcapacitor 508 where they are acted upon by the lower first input biasresistor 506 and the lower second input bias resistor 520 for the lowerchannel, and by the upper first input bias resistor 509 and the uppersecond input bias resistor 521 for the upper channel. After being actedon by these circuit elements, the signals are passed on to the positiveinput of the first lower operational amplifier and the negative input ofthe first upper operational amplifiers 511 and 512 respectively.

By virtue of the fact that the first lower operational amplifier isconnected to the first lower feedback resistor 513, the lower firstderivative resistor 522 and the lower first derivative capacitor 524, itwill accentuate the AC wave forms it passes, and will only pass AC waveforms through the output of the first lower operational amplifier 511.The signal from the output of the first lower operational amplifier 511is then passed onto the positive input of the lower second operationalamplifier 530. The lower second operational amplifier 530 is identicalto the first lower operational amplifier 511 and, in addition, hasidentical components attached to the negative input in the form of thelower second derivative resistor 526, the lower second derivativecapacitor 528 and a lower second feedback resistor 532, so it also willaccept AC wave forms and accentuate these.

At this time, the output from the lower second operational amplifier 530is passed onto the negative input of the lower first comparator 542 ofthe dual first comparator circuit 492. Again, the lower portion of thedual first comparator circuit is identical to the upper portion of thedual first comparator circuit, and the dual first comparator circuit 492in its entirety is identical to the dual second comparator circuit 493.For this reason it is believed necessary to only describe the lowerportion of these circuits which will make clear also then the operationof the upper portion of the circuits to one skilled in the art.

At the same time the negative input of the lower first comparator 542 isreceiving a signal from the output of the lower second operationalamplifier 530, the positive input of the lower first comparator 542 isreceiving an input through the lower second set point resistor 538 andthe upper second set point resistor 540. This will produce an outputfrom the lower first comparator 542 which will be modified by virtue ofthe connection in parallel between the output of the lower firstcomparator and the positive input thereof of the lower third feedbackresistor 544 and the lower first feedback capacitor 546. Thisarrangement is known to those skilled in the art as a "Schmitt triggeredcomparator" and the practical effect of this is to cause the output ofthe lower first comparator to suddenly go very high or very low, andvery rapidly.

This output from the lower first comparator 542 is supplied to thenegative input of the lower second comparator 552. Similarly to thatjust described, the positive input of the lower second comparator 552 isreceiving an input through the lower fourth set point resistor 550 andthe lower third set point resistor 548. This again produces an outputwhich, because of an identical Schmitt triggering arrangement, by virtueof the connection in parallel of the lower four feedback resistor 554and the lower second feedback capacitor 556, will again go very high orvery low in a rapid manner. The output from the lower second comparator552 then is inputted into the input of the lower receive latch 477.

As mentioned previously, the lower receive latch is receiving power fromthe power supply circuit, and is also receiving a signal from thesynchronous modulator driver transistor 473.

As was previously described, if the light emitting diode of thetransmitter is run continuously, it cannot be run at a very high level,and a much higher level output is achieved if the light emitting diodeis pulsed intermittently. For this to be sensibly used in the system, wealso need only have our receiver circuit look to see if light is beingtransmitted at the same time the diode is being pulsed. It is thissignal from the synchronous modulator driver transistor to the decodercircuit which allows us to look at the diode at the same time it isbeing pulsed to see if the light signal coming from the light emittingdiode is blocked by the float. Thus, the lower latch 477 acts tosynchronize the input sampling with the LED output.

The Q output of the lower receive latch 477 is supplied to one input ofthe low AND gate 558. While the Q bar output of the same latch issupplied to one input each of the in-band AND gate 559 and the high ANDgate 560.

To supply the other inputs to the low, in-band and high AND gates 558,559 and 560 respectively, for proper operation thereof, it is necessaryto have an input to these AND gates from the upper latch 478. Thisoutput is produced in the manner substantially identical to that justdescribed for the lower latch 477 by virtue of the signals coming intothe upper portion of the dual first amplifier circuit 490 and beingacted on in exactly the same manner described for the lower portion ofthe dual first amplifier circuit. Thus, it is only believed necessary tostate that the upper portion of the dual first amplifier circuitconsists of the first upper operational amplifier 512, the first upperfeedback resistor 514, the upper first derivative resistor 523 and theupper first derivative capacitor 525. Again, as before, the output fromthe first upper operational amplifier will be supplied to the positiveinput of the upper second operational amplifier 531.

Again, the operations which take place in the upper portion of the dualsecond amplifier circuit are exactly the same as those which have beenpreviously described as taking place in the lower portion of the dualsecond amplifier circuit. Therefore, it is again believed only necessaryto state that the components of the dual second amplifier circuitconsist of the upper second derivative resistor 527, the upper secondderivative capacitor 529, the upper second operational amplifier 531,and the upper second feedback resistor 535. This produces an output fromthe upper second operational amplifier exactly the same as that from thelower second operational amplifier 530, and this is passed on in amanner exactly the same as before to the negative input of the upperfirst comparator 543.

Again, the upper portion of the dual first comparator circuit 492 isexactly identical to the lower portion of the dual first comparatorcircuit 492, and exactly the same operations take place. Thus, it isdeemed only necessary to state that the components of the upper portionof the dual first comparator circuit consist of the upper first setpoint resistor 537, the upper second set point resistor 540, the upperfirst comparator 543, the upper third feedback resistor 545 and theupper first feedback capacitor 547.

Again, one comes out of the output of the upper first comparator 543into the negative input of the upper second comparator 553 in the dualsecond comparator circuit 493. Again the upper portion of the dualsecond comparator circuit is exactly the same as the lower portion ofthe dual second comparator circuit and it is only believed necessary tostate that the components of the upper portion of the dual secondcomparator circuit 493 includes the upper third feedback resistor 549,the upper fourth set point resistor 551, the upper second comparator553, the upper fourth feedback resistor 555 and the upper secondfeedback capacitor 557. These components act exactly as they did in thelower portion of the dual second comparator circuit 493 and produce anoutput to the upper receive latch 478.

Exactly as before, the latch has been powered from the power supplycircuit and is receiving a clock signal from the synchronous modulatordriver transistor 473 of the synchronous modulator 462. Again, thisoutput acts exactly the same, and the Q output from the upper receivelatch is supplied to one input each of the low and in-band AND gates 558and 559 respectively, while the Q bar output of the upper receive latch478 is supplied to one of the inputs of the high AND gate 560.

The connections to the high, low and in-band AND gates are designed inaccordance with the desired decoding of the signals received from thetransmitter and receiver 100 and 99 respectively. When the transmitteris to be in-band, one wants a signal to be received by the upperreceiver, but not by the lower receiver so that the float detector 93can follow the top of the float 101. Similarly, when the float is toohigh, both the upper and lower receivers are blocked and when the floatis too low, neither the upper receiver or the lower receiver areblocked.

As can be seen, the output of the AND gates 558-560 are adapted tooperate exactly in this manner and supply the high, low and in-bandsignals to the decode circuit 513 when this occurs. The output from thelow AND gate will be produced only when Q outputs are received from boththe upper and lower latches 478 and 477 respectively. This will onlyhappen when both the lower and upper photo transistors 495A and 495B arereceiving light, which means neither are blocked, which was thecondition for the float being low.

Similarly, an output will be received from the in-band AND gate 559 onlywhen a Q output is received from the upper receive latch and a Q bar isreceived from the lower receive latch 477. Again, this will occur onlywhen one of two signals is being received from the dual input circuitwhich, in turn, can occur only when light is being received by the phototransistor 495 in the upper receiver portion of the float folllower 93which results in the desired Q signal from the upper receive latch 478,which is the condition set forth for the float being in-band.

Since no light is being received by the photo transistor 495A of thelower receiver portion of the float follower 93, there will be no signalbeing passed through the upper portions of the dual input circuit 497,the dual first amplifier circuit 490, the dual second amplifier circuit491, the dual first comparator circuit 492 and the dual secondcomparator circuit 493 so you will get a Q bar output from the lowerreceive latch 477 and thus, both inputs will be provided to the in-bandAND gate 559, which meets the requirements for the float being in-band.

The last case is where the float is high and this would require anoutput from the high AND gate 560 which can only occur when you get a Qbar output from both the lower receive latch 477 and the upper receivelatch 478, which can only occur when no light is being received by lowerphoto transistor 495 and the upper photo transistor 495B.

The output from the high AND gate 560 would be supplied through the highbase resistor 561 and the high output transistor 562 as one of threeinputs to the auto select circuit 402 shown in FIG. 7.

In a like manner, the in-band signal, which is the output from thein-band AND gate 559, would be supplied through the in-band baseresistor 563 and the in-band output transistor 564 as one of the inputsto the auto select circuit, as would the low signal, which is the outputof the low AND gate 558, which would be supplied to the auto selectcircuit through the low base resistor 565 and the low output transistor566. These signals would then be used in the manner previously describedfor automatically tracking the float in our improved flow metercalibration system.

The remainder of the decode circuit 413, which has not been labeled,have been shown with actual component values to allow its duplication byone skilled in the art. It is not believed necessary to describe thesecomponents in detail, as their actual connections are shown and the onlypurpose of this circuit is to provide a convenient way for a technicianto monitor the state of the signals from the receiver 99.

To display the position of the float detector through the float detectorposition display 367, it is first necessary to condition the signal bypassing it through the float detector display circuit 379. A blockdiagram of the float detector display circuit is shown in FIG. 31.

It can be seen that the float detection display circuit consists of a4-1/2 digit display decoder and driver circuit 569 operatively connectedto a five decade BCD counter 571.

It can be noted that the the five decade BCD counter is receiving areset input signal from the manual reset switch 365 (FIG. 11) and isalso receiving an up-down input and a counter input from the displaylatch 572 and display OR gate 573 respectively. The display latch anddisplay OR gate are, in turn, receiving an up count input and a downcount input from the position pulse encoder 97.

The reset input from the manual reset switch 65 has the function ofresetting the five decade BCD counter and thus, the float detectorposition display 367 any time the operator desires to have the displayset to zero.

To count and display the pulses when the system is in operation, it isnecessary to utilize the pulses which form the up count input and thedown count input from the position pulse encoder in a manner to providethe proper input to the five decade BCD counter to enable it to operatethe 4-1/2 digit display decoder and driver circuit.

Since the position pulse encoder produces up count pulses only whenrotating in one direction and down count pulses when rotating in anotherdirection, to supply the signals it is necessary to convert the twooppositive direction pulse trains into a single pulse train and adirection signal. This is done by supplying input from the up countinput, or up pulse train, to the reset input of the display latch and aninput from the down count input, or down pulse train, to the reset inputof the display latch 572. This results in the proper output beingsupplied from the Q output of the display latch to the up-down input ofthe five decade BCD counter 571.

At the same time, it can be seen that either pulse train will be able tosupply a suitable input to cause the display OR gate 573 to provide acount signal to the five decade BCD counter. Thus, it can be seen, forexample, with the position pulse encoder 97 operating in a direction soas to supply an up count input, an input would be supplied to thedisplay latch causing an up polarity signal to be supplied to the fivedecade BCD counter.

We have already in general described the mechanics of the weigh scale ofour present invention, but certain additional features should bedescribed, which are important to our invention.

It should be known that in constructing our scale we started with thestandard Tridyne scale which is commercially available as Model No.410-1052 manufactured by the Tridyne Corporation. This scale came withthe standard base 600, the large platform support 594, the smallplatform support 595, the lower beam 597 and the upper beam 596. To thiswe added the encoder 260, the counterweight 599, the ball screw 170, thepoise weight and ball nut assembly 171 and the poise motor 262, togetherwith the large flow bucket 163 and the low flow bucket 164 previouslydescribed.

With regard to the ball screw, it should be understood that a veryaccurate ball screw with a very fine thread was found to be necessary toprovide the desired degree of calibration for accurate weighing. Theball screw which we chose after much experimentation is one manufacturedby Beaver Precision Products, their Model No. PO805 20-pitch ball screw.The ball screws we tried previous to this simply were not accurateenough for our purposes.

A drain assembly 588 is provided as shown in case of overflow fromeither the high flow bucket 163 or the low flow bucket 164. Manyfeatures of the injection system and extraction system have already beendescribed, but one feature which is important which is not previouslybeen described is the shape of the smooth flow tube assembly 589.

It can be seen that the rakish angle at the end of the assembly, plusthe shape of the discharge deflectors at the end thereof, are intendedto minimize kinetic energy effects, as are the wool mesh kinetic energyabsorption devices 590 and 591 respectively.

With respect to the extraction systems, it should be noted that the highflow extraction tube assembly 165 and the low flow extraction tubeassembly 166 retract during the test cycle to eliminate the buoyancyeffect which they otherwise would have.

To prevent any drippage from occurring when they are retracted, whichwould effect the measuring result, it should be noted that a high flowevacuation valve seat 583 is provided on the end of the flow lift rodproviding part of the assembly. The lift rod 582 is sealed by a highflow evacuation seal 584.

Similarly, a low flow evacuation valve seat 586 is provided on the endof the low flow lift rod 587 which is sealed by a low flow evacuationseal 587. This concludes the description of the mechanical features ofour scale which are necessary to effectuate the accurate measurementsneeded in our system.

Another portion of the mechanics of our system which warrantsexplanation is the means for tracking the float 101 in the glass tubeflow meter 78.

One may refer to FIGS. 45, 46, 47 and 48 for a detailed illustration ofthe mechanical apparatus which moves the float follower 93, and thus thetransmitter 100 and the receivers 99A and 99B up and down the flow tube78. These devices consist of a pair of vertical support rods 604attached between an upper platform 602 and a lower platform 603.

The upper platform supports a stepper motor 95 which operates the ballscrew 96 through the gear train 601. The opposite end of the ball screw96 drives the encoder 97. Vertical movement of the float follower 93 isprovided by the turning of the ball screw 96, driving the assembly upand down the vertical rods 604. Bushings 609 are provided in the floatfollower support guide 608 for ease of movement. The bushings 609 at theextremity of the support guide are driving the assembly up and down thevertical rod 604, bushings 609 in the float detector support guide 608to apply for ease of movement and the bushings 609 at the extremity ofthe support guide is identical to the other bushings to provide athree-point support.

A part of the float follower 93 is allowed to pivot about the pivotassembly 610 so that it may be pivoted into and out of engagement withthe flow tube 78. In order that the pivoted portion of the follower 93may be maintained in an upright position while it is positioned, themagnetic latch 611 is provided.

The float follower 93 may be locked in any desired position along theguide rod 604 by means of the pivot lock 612.

The actual transmitter 100 and receiver 99 are mounted on a pair offloat detector jaws 613 by means of the spring loaded assemblies 614.This allows the operator to space the jaws 613 and pivot the assemblyout of the way when calibration is finished, and allows for the initialplacement of the jaws about the flow meter 78.

Further, it provides for keeping the transmitter 100 and the receiver 99centered during the travel of the float detector up and down the lengthof the flow tube 78.

To provide for horizontal movement of the float detector, generallydesignated by the numeral 93, in order to calibrate one or more flowtubes, the entire float detector may be moved horizontally by virtue ofthe ball bushings 614 which travel along the horizontal guide rod 607.

After having now described the circuitry and mechanics of our flow metercalibration system we are now able to describe the typical operation ofour improved flow meter calibration system.

In a typical operation, the operator will first desire to turn on thehydraulic system before taking other setup procedures, and this wouldinvolve turning the system on by means of the off-on switch 178, whichwould cause the pilot light 179 to illuminate. The on button 181 wouldbe depressed to supply power to the control panel 179, the supply pumpwould be turned on by depressing a supply pump switch 182, the operatorwould turn on the supply pump by means of the supply on-off switch 182,turn on the evacuation pump by means of the evacuation pump on-offswitch 184, and turn on the fuel temperature control switch 195, andwould also turn on the injectors 159 and 160 in a manner previouslydescribed by depressing the injector on-off switch 196 which alsoactivates the fuel injector pressure transducer 151 and the fluid inletpressure display 156. By this sequence of operation, the temperaturedisplay 152 will have been activated.

This sequence of operation will start the proper subsystems operating tobring the calibration fluid to the proper temperature. This operation isstarted first since it takes some time, and now allows the systemoperator to mount the flow meter to be calibrated and place the floatfollower 93 about the flow meter tube 78, which is desired to becalibrated.

As before, this involves moving the float follower either horizontallyon the horizontal guide rods 607 and/or vertically on the vertical guiderod 604, and then pivoting down the pivoted portion, and then pivotingthe pivoted portion of the float follower 93 into the position about thepivot 610 by holding the float follower jaws 613 apart. When thetransmitter 100 and the receiver 99 have been properly lined up on theflow tube 99, the jaws are released gently so that the jaws will engagethe flow tube.

Having now engaged the flow meter to be calibrated, if the temperatureof the fluid has reached the desired operating temperature, we are nowready to activate the float detection subsystem of the present inventionby depressing the float detection on-off switch 364, and operating themode select switch 363, to place the system in a manual mode ofoperation by means of the previously described circuitry.

As described hereinbefore, to put the system in automatic mode tocalibrate the glass flow tube 78 in several positions, it is firstnecessary to set the float detector 93 to lock on the reference line158.

By means of the circuitry previously described, and the logic built intothe system, it is necessary for the float to be placed either below thereference line, or preferably, above the reference line before this. Inaddition to the float being above the reference line, the operatorshould make certain that the float follower 93 is above the referenceline, but below the float. To do this, the operator may use any of thejog up, jog down, slow up, slow down, fast up or fast down buttons372-377 respectively.

Once the operator has the float follower 93 above the reference line,but below the float, he will depress the auto setting on the mode selectswitch 363 and the auto start switch 371, placing the system in anautomatic mode of operation by virtue of the circuitry previouslydescribed. Because of the logic built into the system, the floatfollower 93 will proceed in a downward direction until it reaches thereference line and then will lock onto said reference line 158.

The operator will then push the reset switch 65 to reset the floatdetector position display 367 to zero so that the movement of the floatdetector will give a position in inches from the reference line.

The operator, before proceeding further, must turn on the weigh scalesubsystem of the present invention by depressing the scale power on-offswitch 248 to supply power to the weigh scale subsystem previouslydescribed. Again, to ensure accurate operation, and to take into accountthe temperature errors due to warm-up, etc., the operator should wait asufficient length of time for the temperature in the weigh scale systemto stabilize.

Assuming now that the weigh scale subsystem has had sufficient warm-uptime, the float will most probably be at an unknown position, and theoperator must again depress the auto position on the mode select switch363 to enable him to manually move the float detector 93, and he maymost advantageously do this by pressing the fast up switch 376, andvisually observe the movement of the float detector in an upwarddirection until it has surpassed the position of the float.

At this time the operator will immediately press the auto start buttonand will then immediately push the auto position of the mode selectswitch 363 to place the system in automatic operation which alsorequires depressing the auto start switch. It will be remembered thatbecause of the logic built into the circuit, the float detector 93 willnow travel again in a downward direction, until it finds the float, andat this point it will stop and track the float with no further effort onthe part of the operator.

It is at this point that the great advantage of our flow metercalibration system becomes obvious, as the operator can now, if he hasnot already utilized the duty cycle switches 81 and the period switches84, use the switches as previously described to set a wide of range onthe flow meter and produce a reading of the float position with regardto the fixed reference line for each such flow which will enable him,upon completion of the test, to prepare a scale indicating thereon flowas a function of distance from the reference line in an extremelyaccurate manner.

Before the test can actually start, the operator, if he has not alreadydone so will select the pretest time for the purposes previouslydescribed on the pretest switch 245, set the test time on the test timeselect switch 246 and select minutes or seconds on the test time unitselect switch 247.

The pretest and the test time depend on user requirements and need to belearned by experience. We have found that a pretest time of from ten tofifteen seconds is usually sufficient.

The time of test depends on several factors. Since there is only limitedflow bucket capacity and flow travel, one must make certain that thetest time is not set too long to overflow the system, but, on the otherhand, for low flow rates, one will need a longer test than one will needfor the shorter test.

It becomes obvious because of the wide range of settings available ofboth the weigh scale system and injector system that a practicallyinfinite number of points can be calibrated on any given flow meter.

Thus, by abandoning the old fixed weight-variable time flow metercalibration system, and inventing the novel variable weight-fixed timesystem, we have provided a novel and extremely accurate method andapparatus for calibrating flow meters at a wide range of flows,including very low flows.

We claim:
 1. A float detection system for detecting the position of afloat in a glass tube flow meter undergoing calibration, said floatdetection system including:(a) a means for tracking said floatoperatively mounted adjacent to said glass flow tube; (b) a ball screwoperatively connected to said means for tracking said float to move itin an axial direction; (c) a stepper motor connected to said ball screwto operate the same; (d) a pulse encoder attached to the other end ofsaid ball screw; (e) a pulse encoder circuit to produce pulses relatedto the rotation of said ball screw; (f) a float detector display circuitconnected to said pulse encoder to indicate the position of said meansto track said float; (g) a float detector position display connected tosaid float detector display circuit to display the position of saidfloat detector; (h) an optical conditioner circuit connected to saidmeans to track said float to supply power thereto; (i) a stepper drivercircuit adapted to supply appropriate signals to said stepper motor; (j)a float detector control circuit adapted to receive signals from saidoptical conditioner circuit and to utilize them to supply signals tosaid stepper driver circuit; and (k) a travel limit circuit connected tosaid float detector control circuit.
 2. The device defined in claim 1,wherein said means for tracking said float includes:(a) an upperplatform with said stepper motor mounted thereto; (b) a lower platformwith said optical encoder mounted thereto, said ball screw being mountedbetween said stepper motor and said optical encoder; and (c) a pair ofvertical support rods attached between said upper platform and saidlower platform.
 3. The device defined in claim 2, wherein said means totrack said float further includes:(a) a float follower apparatusoperatively mounted to said vertical support rods for movement in avertical direction adjacent said glass flow tube.
 4. The device definedin claim 3, wherein said float follower apparatus further includes:(a) afloat follower support guide mounted on said float follower apparatusand adapted to fit over said vertical support rod; (b) at least onebushing interposed between said vertical support rod and said floatfollower support guide to aid in the vertical movement thereof; and (c)at least one bushing interposed between the other of said vertical rodsand said float follower also to aid in the vertical movement thereof. 5.The device defined in claim 4, wherein said float follower apparatusincludes:(a) a pivoted portion adapted to pivot about a pivot assemblyin order that the pivoted portion of the float follower apparatus may bepivoted into and out of engagement with said glass flow tube.
 6. Thedevice defined in claim 5, wherein said pivot portion includes:(a) amagnetic latch adapted to maintain said pivoted portion in an uprightposition when desired.
 7. The device defined in claim 6, and including apivot lock adapted to lock said float follower in any desired positionalong said guide rod.
 8. The device defined in claim 7, wherein saidupper and said lower platforms are operatively and movably mounted to apair of horizontal rods for movement in the horizontal direction.
 9. Thedevice defined in claim 8, wherein said pivoted portion of said floatfollower apparatus includes:(a) a pair of float detector jaws adapted tofit about said glass flow tube; and (b) a pair of spring loadedassemblies operatively connected to said spring loaded jaws to allowmovement thereof into and out of engagement with said glass flow tube.10. The device defined in claim 4, wherein one of said float detectorjaws has a transmitter operatively mounted thereon.
 11. The devicedefined in claim 10, and including a receiver mounted on the other ofsaid spring loaded jaws.
 12. The device defined in claim 11, whereinsaid receiver includes:(a) a high receiver; and (b) a low receiver. 13.The device defined in claim 12, wherein said high receiver includes:(a)a surface adapted to be adjacent a photo transistor; (b) a surfaceadapted to be adjacent said float; and (c) fiber bundles embedded insaid high receiver and having a narrow rectangular cross section wheresaid fiber bundles exit from said surface adapted to be adjacent saidfloat, and a cylindrical cross section where said fiber bundles exitfrom said surface adapted to be adjacent said photo transistor.
 14. Thedevice defined in claim 13, wherein said low receiver includes:(a) asurface adapted to be adjacent a photo transistor; (b) a surface adaptedto be adjacent said float; (c) fiber bundles embedded in said lowreceiver and having a rectangular cross section where said fiber bundlesexit from said surface adapted to be adjacent said float; and (d) acylindrical cross section where said fiber bundles exit from saidsurface adapted to be adjacent said photo transistor.
 15. The devicedefined in claim 14, wherein said receiver includes:(a) an optical headhaving an upper photo transistor adapted to be adjacent said cylindricalcross section of said fiber bundle in said upper receiver; and (b) alower photo transistor adapted to be adjacent said cylindrical crosssection of said fiber bundle in said lower receiver.
 16. The devicedefined in claim 15, wherein said float detector control circuitincludes:(a) a manual select and input circuit; (b) a clock speed selectcircuit operatively connected to said manual select and input circuit;(c) a clock circuit having slow and fast outputs connected to said clockspeed and select circuit; (d) a direction polarity latch circuitconnected to said manual select and input circuit and said clock speedselect circuit; (e) an auto select circuit connected to said manualselect and input circuit and said clock speed select circuit and saiddirection polarity latch circuit; (f) an auto select circuit connectedto said clock speed select circuit and said direction polarity latchcircuit; (g) an auto abort circuit connected to said auto selectcircuit, said direction polarity latch circuit, said clock speed selectcircuit and said clock circuit, and connected to said opticalconditioner circuit; and (h) a stepper motor translator circuit conectedto said direction polarity latch circuit and said stepper drivercircuit.
 17. The device defined in claim 16, wherein said float detectordisplay circuit includes:(a) a four and one-half digit display decoderand driver circuit connected to a float detector position display; (b) afive decade BCD counter having a reset input, up-down input and countinputs and having an output, with said output adapted to be conected tothe input of said four and one-half digit display decoder and drivercircuit; (c) a display latch having set and reset inputs and an up-downoutput, with said up-down output connected to the up-down input of saidfive decade BCD counter; and (d) a display OR gate having two inputs andan output, with the output thereof connected to the count input of saidfive decade BCD counter and the inputs thereof being connected to theset and reset inputs of said display latch and adapted to receivesignals from said pulse encoder.
 18. The device defined in claim 17,wherein said optical conditioner circuit includes:(a) an amplifiercircuit having inputs and outputs; (b) a power supply circuit connectedto said amplifier circuit; (c) a synchronous modulator connected to saidpower supply; and (d) a decode circuit connected to said amplifiercircuit and to said synchronous modulator.